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We claim:
1. A cordless telephone, comprising:
a base unit connectable to a telephone network line for receiving and
transmitting signals therethrough;
a handset unit selectively mountable upon and separable from said base
unit;
said base and handset units including respective means for the transmission
and reception of signals therebetween over electromagnetic waves, said
handset unit further including handset loudspeaker/microphone means and
said base unit having base loudspeaker/microphone means associated
therewith;
said telephone having a telephone mode of operation, wherein the
loudspeaker/microphone means of either said base unit or said handset unit
is in communication with said telephone network line, and an intercom mode
of operation, wherein said handset and base loudspeaker/microphone means
are in communication with each other;
means for selectively establishing one of said telephone and intercom
modes;
call detecting means for detecting an incoming telephone call appearing on
said telephone network line and for producing a detected signal in
response thereto;
first bell sound generating means at said base unit for generating a first
bell sound in response to said detected signal at least in said intercom
mode;
second bell sound generating means at said handset unit for generating a
second bell sound in response to said detected signal at least in said
intercom mode; and
intercom stop means receiving said detected signal and being then
selectively actuable at one of said base and handset units so as to be
operative in said intercom mode for causing said first and second bell
sound generating means to cease generating said first and second bell
sounds, respectively, and for causing said means for selectively
establishing one of said modes to establish said telephone mode with the
loudspeaker/microphone means of the other of said base and handset units
in communication with said telephone network line.
2. A cordless telephone according to claim 1, wherein said base
loudspeaker/microphone means is included in a standard telephone having a
receiver and a cradle, and said intercom stop means is actuated at said
base unit by the mounting of said receiver onto said cradle.
3. A cordless telephone according to claim 1, wherein said intercom stop
means includes first switch means actuable at said base unit and second
switch means actuable at said base unit.
4. A cordless telephone according to claim 1, further comprising connection
means for selectively connecting said base and handset
loudspeaker/microphone means with said telephone network line and each
other, said means for selectively establishing one of said modes supplying
a plurality of connection control signals to said connection means to
control the operation thereof.
5. A cordless telephone according to claim 4, wherein said connection means
includes relay means for selectively connecting any two of said means for
the transmission and reception of signals of said base unit, said base
loudspeaker/microphone means and said telephone network line in response
to said connection control signals.
6. A cordless telephone according to claim 1, wherein said intercom stop
means includes base and handset components, said base component is
operative upon actuation of said intercom stop means at said base unit
after receipt of said detected signal for supplying a first control signal
to said first bell sound generating means to cause the same to cease
generating said first bell sound and for supplying a second control signal
to said handset component, and said handset component is responsive to
said second control signal for supplying a third control signal to said
second bell sound generator to cause the same to cease generating said
second bell sound.
7. A cordless telephone according to claim 6, wherein said handset
component is operative upon actuatlon of said intercom stop means at said
handset unit after receipt of said detected signal for supplying said
third control signal to said second bell sound generating means to cause
the same to cease generating said second bell sound and for supplying a
fourth control signal to said handset component, and said handset
component is responsive to said fourth control signal for supplying said
first control signal to said first bell sound generating means for causing
the same to cease generating said first bell sound.
8. A cordless telephone according to claim 7, further comprising connection
means for selectively connecting said base and handset
loudspeaker/microphone means with said telephone network line and each
other in response to connection control signals supplied thereto; and
said base component is further operative upon said subsequent actuation at
said base unit for supplying a first connection control signal to said
connection means to cause the same to connect said handset
loudspeaker/microphone means to said telephone network line.
9. A cordless telephone according to claim 8, wherein said base component
is responsive to said fourth control signal for supplying a second
connection control signal to said connection means to cause the same to
connect the base loudspeaker/microphone means to said telephone network
line.
10. A cordless telephone according to claim 1, wherein said handset unit
has talk and standby modes of operation wherein said means for selectively
establishing one of said telephone and intercom modes is enabled and
disabled, respectively;
actuable switch means at said handset unit for selectively establishing one
of said talk and standby modes; and
said second bell sound generating means is responsive to said modes of said
handset unit and said telephone so as to generate said second bell sound
at a first volume in said standby mode and at a second, lesser volume when
said handset unit is in said talk mode while the telephone is in said
intercom mode.
11. A cordless telephone according to claim 10, wherein actuation of said
switch means in said talk mode to establish said standby mode actuates
said intercom stop means at said handset unit.
12. A cordless telephone according to claim 10, wherein said switch means
has a first position for establishing said standby mode and a second
position for establishing said talk mode and said second bell sound
generating means includes second switch means ganged with the first
mentioned switch means and having corresponding first and second positions
for controlling said volume in accordance with the position of said first
switch means.
13. A cordless telephone according to claim 12, wherein said second bell
sound is produced through said handset loudspeaker/microphone means;
said second switch means in said first position provides said second bell
sound directly to said handset loudspeaker/microphone means, and in said
second position provides said second bell sound to said handset
loudspeaker/microphone means through an attenuating means.
14. A cordless telephone, comprising:
a base unit connectable to a telephone network line for receiving and
transmitting signals therethrough;
a handset unit selectively mountable upon and separable from said base
unit;
said base and handset units including respective means for the transmission
and reception of signals therebetween over electromagnetic waves, said
handset unit further including handset loudspeaker/microphone means and
said base unit having base loudspeaker/microphone means associated
therewith;
said telephone having a telephone mode of operation, wherein the
loudspeaker/microphone means of either said base unit or handset unit is
in communication with said telephone network line, and an intercom mode of
operation, wherein said handset and base loudspeaker/microphone means are
in communication with each other;
means for selectively establishing one of said telephone and intercom
modes;
said handset unit having talk and standby modes of operation wherein said
means for selectively establishing one of said telephone and intercom
modes is enabled and disabled, respectively;
actuable switch means of said handset unit for selectively establishing one
of said talk and standby modes;
call detecting means for detecting an incoming telephone call appearing on
said telephone network line and for producing a detected signal in
response thereto;
first bell sound generating means at said base unit for generating a first
bell sound in response to said detected signal at least in said intercom
mode;
second bell sound generating means at said handset unit responsive to said
detected signal for generating a second bell sound at a first volume in
said standby mode and at a second, lesser volume when said handset unit is
in said talk mode while the telephone is in said intercom mode;
said first and second bell sound generating means being further responsive
to said modes of the telephone so that, at a time when said telephone is
in said intercom mode and said first and second bell sound generating
means are generating said bell sounds, change-over to said telephone mode
causes said first and second bell sound generating means to cease
generating the respective bell sounds.
15. A cordless telephone according to claim 14, further comprising
intercom stop means receiving said detected signal and being then
selectively actuable at one of said base and handset units operative in
said intercom mode for causing said first and second bell sound generating
means to cease generating said first and second bell sounds, respectively,
and for causing said means for selectively establishing one of said modes
to establish said telephone mode with the other of said base and handset
units in communication with said telephone network line.
16. A cordless telephone according to claim 15, wherein actuation of said
switch means in said talk mode actuates said intercom stop means at said
handset unit.
17. A cordless telephone according to claim 14, wherein said second bell
sound generating means includes volume control means responsive to the
existing mode of said handset unit for selecting one of said first and
second volumes.
18. A cordless telephone according to claim 17, wherein said switch means
has a first position for establishing said standby mode and a second
position for establishing said talk mode, and said volume control means
includes second switch means ganged with the first mentioned switch means
and having corresponding first and second positions for selecting one of
said first and second volumes.
19. A cordless telephone according to claim 18, wherein said second bell
sound is produced through said handset loudspeaker/microphone means;
said second switch means in said first position providing said second bell
sound directly to said handset loudspeaker/microphone means, and in said
second position providing said second bell sound to said handset
loudspeaker/microphone means through an attenuating means. |
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Claims |
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Description |
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RELATED APPLICATIONS
U.S. patent application Ser. No. 06/696,183, filed Jan. 29, 1985 in the
name of persons having an obligation of assignment to the assignee of the
present invention and commonly assigned herewith, U.S. patent application
Ser. No. 722,359, filed 4-12-85, in the name of persons having an
obligation of assignment to the assignee of the present invention and
commonly assigned herewith, U.S. patent application Ser. No. 725,341,
filed 4-19-85, in the name of persons having an obligation of assignment
to the assignee of the present invention and commonly assigned herewith.
FIELD OF THE INVENTION
The present invention relates generally to cordless telephones, and in
particular relates to a cordless telephone operable in an intercom mode.
BACKGROUND OF THE INVENTION
The standard telephone consists of a base unit and a handset unit connected
to each other by an electrical cord. The base unit itself is connected by
another cord to a receptacle on a wall, telephone pole or a similar
immovable structure to which the telephone network line extends.
Therefore, the range of movement of the operator of the telephone is quite
limited. Even when the cords connecting the handset unit to the base unit
and the base unit to the wall are long, it can be cumbersome to move
either the entire telephone around to make calls from different locations
or to walk around with the handset unit once a call has been placed. The
simple fact that there is always a continuous physical connection between
the person making the phone call and the immovable wall or other fixed
structure can be a great inconvenience.
The cordless telephone represents a significant improvement over the
standard telephone. In the conventional cordless telephone, the base unit
is still connected to the receptacle on the immovable wall or the like by
a cord so that message signals from the telephone network line may be
received and transmitted. However, the handset unit of the cordless
telephone is an independently operative unit from which calls may be made
and by which calls may be received with no physical connection to the base
unit. Instead, the base unit and the handset unit of the cordless
telephone communicate with each other over a communication channel
established by the transmission and reception of electromagnetic waves,
conventionally radio waves. The handset unit may then be taken to
distances of up to 300 meters from the base unit, while still making and
receiving telephone calls.
The handset unit has a transmitting/receiving system or transceiver and a
loudspeaker in the earpiece and a microphone in the mouthpiece. In some
cordless telephones, the base unit also has a loudspeaker and microphone
either incorporated within the base unit itself or in an auxiliary
standard telephone connectable to both the base unit and the outside
telephone network line. When the base unit receives an incoming call, the
base loudspeaker/microphone can be used to converse directly with the
caller.
Two modes of operations are possible. In the telephone mode of operation,
either the base unit or the handset unit is in communication with the
outside telephone network line, and in the intercom mode of operation, the
base unit and the handset unit are in communication with each other. This
makes operation of the cordless telephone very convenient.
When such an intercom mode is available, there is the possibility that an
incoming telephone call will appear when the cordless telephone is in the
intercom mode. To announce the presence of the incoming call, both the
handset unit and the base unit will ring. The handset unit conventionally
rings by producing a ringing sound from its loudspeaker. When the handset
operator is talking to the base operator, he is holding the handset unit
with the loudspeaker directly next to his ear. The normal ringing sound
could be unpleasant or painfully loud under these circumstances.
Prior art cordless telephones of this type have had a mode switch on the
base unit which is actuated when an incoming call appears in the intercom
mode to cause a changeover from the intercom mode to the telephone mode
with the base unit in communication with the telephone network line.
However, the operation of such prior art mode switches has been
inconvenient and unduly complicated, leading to a likelihood of
misactuation by those who are unfamiliar with cordless telephones in
particular and electronic devices in general. It would be advantageous to
provide a cordless telephone with an operation so simple that it is
unnecessary to understand how it works in order to operate it
successfully.
A further disadvantage of the described prior art cordless telephone is
that only the base operator can answer the incoming telephone call since
the mode switch is provided only on the base unit. This limits the
flexibility of the cordless telephone.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an
improved cordless telephone which eliminates the difficulties of the prior
art.
It is another object of the present invention to provide a cordless
telephone in which either one of the handset and base units may receive an
incoming telephone call which appears when the telephone is in the
intercom mode.
It is another object of this invention to provide a cordless telephone in
which, if an incoming call appears when the telephone is in the intercom
mode of operation, either of the handset and base units may be actuated to
withdraw from the intercom mode and automatically connect the other of the
units with the telephone network line to receive the incoming telephone
call.
It is a further object of this invention to provide a cordless telephone
which generates a ringing sound with a low volume when the telephone is in
the intercom mode.
It is still another object of the present invention to provide a cordless
telephone with the aforesaid capabilities which may be operated easily and
conveniently.
It is yet another object of the present invention to provide a cordless
telephone with the aforesaid capabilities having a minimum number of
actuable switches for performing these functions.
In accordance with an aspect of the present invention, there is provided a
cordless telephone comprising a base unit connectable to a telephone
network line for receiving and transmitting signals therethrough, and a
handset unit selectively mountable upon and separable from the base unit.
The base and handset units have respective transceiver means for the
transmission and reception of signals therebetween over electromagnetic
waves, the handset unit including handset loudspeaker/microphone means and
the base unit having base loudspeaker/microphone means associated
therewith. The telephone has a telephone mode of operation wherein the
loudspeaker/microphone means of either of the base unit or the handset
unit is in communication with the telephone network line, and an intercom
mode of operation, wherein the base and handset loudspeaker/microphone
means are in communication with each other, and means for selectively
establishing the telephone in one of the telephone and intercom modes are
provided. Call detecting means detects an incoming telephone call
appearing on the telephone network line to produce a detected signal in
response thereto. First bell sound generating means at the handset unit
generates a bell sound in response to the detected signal at least in the
intercom mode, and second bell sound generating means at the handset unit
generates a second bell sound in response to the detected signal at least
in the intercom mode. Intercom stop means receive the detected signal and
are then selectively actuable at one of the handset and base units so as
to be operative in the intercom mode for causing the first and second bell
sound generating means to cease generating the first and second bell
sounds, respectively, and for causing the means for selectively
establishing the telephone in one of the modes to establish the telephone
mode with the loudspeaker/microphone means of the other of the base and
handset units in communication with the telephone network line.
In accordance with another aspect of the present invention, the handset
unit has talk and standby modes wherein the means for selectively
establishing one of the telephone and intercom modes is enabled and
disabled, respectively, and actuable switch means are provided for
selectively establishing one of the talk and standby modes. The handset
bell sound generating means is responsive to the detected signal from the
call detecting means to generate the second bell sound at a first volume
in the standby mode and at a second, reduced volume when the handset unit
is in the talk mode while in the intercom mode of the telephone. The
lesser volume of the second bell sound avoids producing a painfully loud
noise directly in the ear of the handset operator.
In a preferred embodiment of the cordless telephone according to the
present invention, the base loudspeaker/microphone means are constituted
by an auxiliary standard telephone connectable to both the telephone
network line and the base unit. The intercom stop means in this embodiment
includes the conventional switch within the standard telephone actuated
when the receiver is returned to its cradle.
In a another preferred embodiment of the cordless telephone according to
the present invention, the base loudspeaker/microphone means is
incorporated within the base unit itself, and the intercom stop means
includes an actuable switch and relay circuits within the base unit.
The above, and other objects, features and advantages of the cordless
telephone according to the present invention will become apparent from the
following detailed description of the preferred embodiments and the
accompanying drawings, throughout which like reference numerals designate
like elements and parts.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a cordless telephone of a type to which the
present invention may be applied, and with a handset unit being shown
separated from a base unit;
FIG. 2 is a block diagram illustrating a portion of the circuitry of a
handset unit of a cordless telephone according to a first preferred
embodiment of the present invention;
FIG. 3 is a block diagram illustrating a portion of the circuitry of a base
unit of the cordless telephone according to the first preferred
embodiment;
FIG. 4 is a flowchart of a control program of the base unit of FIG. 3 when
either of the base and handset units is operative in the intercom mode for
receiving an incoming telephone call; and
FIG. 5 is a block diagram illustrating a portion of the circuitry of a
handset unit of a cordless telephone according to a second preferred
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings in detail, and initially to FIG. 1 thereof, a
cordless telephone 10 of a type to which the present invention may be
applied is there shown to include a handset unit 1 and a base unit 2. Base
unit 2 is connected by a telephone cord 3 to an outlet or receptacle in a
wall, a telephone pole, or another fixed structure, so that it may both
receive and transmit telephone message signals through a telephone network
line 3a and also may be powered thereby. An antenna 100 on handset unit 1
and a corresponding antenna 200 on base unit 2 are used to create a
communication channel between the two units by the transmission and
reception of radio waves, schematically illustrated in FIG. 1 by the
arrows extending between the antennas. As is conventional, handset unit 1
includes a ten-key panel 151 for making or dialing outgoing calls, and a
mouthpiece 101 and an earpiece 102 with which a microphone and a
loudspeaker (not shown) are, respectively, associated. A telephone number
may be entered on ten-key panel 151, and corresponding information is
transmitted over the communication channel to base unit 2 and thence to
telephone network line 3a. Alternatively, when base unit 2 receives a
message signal from the telephone network line indicating that an incoming
call is present, a signal from base unit 2 causes a ringing sound in
handset unit 1 and a second ringing sound in base unit 2 to indicate the
existence of the incoming call.
The standard maximum separation of such a handset unit 1 and base unit 2,
which is called the service area, is about 300 meters, and is set by the
Federal Communications Commission. Typically there are ten duplex channels
permitted for each system, with the upper channel having a frequency in
the 49 MHz band and the lower channel having a frequency in the 46 MHz
band. Of course, such operating parameters are set by the FCC and do not
form a part of the present invention.
Before describing the structure and operation of cordless telephone 10
according to the present invention, the operating modes thereof will be
described. In a telephone mode of operation, a selected one of the base
and handset loudspeaker/microphone means is in communication with
telephone network line 3a. In an intercom mode of operation, the base and
handset loudspeaker/microphone means are in communication with each other
and not in communication with telephone network line 3a. Any incoming
telephone call appearing on telephone network line 3a is held by a
suitable connection device, conventionally including relays, and is
available should cordless telephone 10 be subsequently established in the
telephone mode. It is possible for cordless telephone 10 to be established
in the intercom mode without an incoming telephone call appearing on
telephone network line 3a, and for an incoming telephone call to then
appear on telephone network line 3a. Cordless telephone 10 according to
the present invention is advantageously adapted to receive an incoming
telephone call which appears when the telephone is in the intercom mode.
Referring now to FIGS. 2 and 3, important portions of the circuitry
contained within handset unit 1A and base unit 2A, respectively, of a
cordless telephone according to the present invention are therein
illustrated. It should be noted that the circuitry within these two units
contains many corresponding elements, so that the two figures and their
accompanying description should be considered together.
Handset unit 1A (FIG. 2) has a transceiver which includes a transmission
system 110 comprised of elements bearing reference numerals 111 to 115,
and a receiving system 120, comprised of elements bearing reference
numerals 121 to 128. Base unit 2A (FIG. 3) similarly has a transceiver
which includes a transmission system 210 comprised of elements bearing
reference numerals 212 to 215, and a receiving system 220 comprised of
elements bearing reference numerals 221 to 227. Base unit 2A further
includes a connecting circuit 230, including elements 231 and 232, and
serving to connect the transmission system 210, the receiving system 220
and an auxiliary telephone 4 to telephone network line 3a. In a first
preferred embodiment, auxiliary telephone 4 having a body 4a and a
receiver 4b is used as the loudspeaker/microphone or electro-audio
transducer associated with base unit 2A. For a better understanding of the
present invention, the function and operation of these elements will be
described as signals are transmitted between the two units. In the
illustrated embodiment, the signals are transmitted over a selected one of
two allowed duplex channels, A and B, each containing an upper channel and
a lower channel.
Therefore, for the transmission of a signal from handset unit 1A (FIG. 2),
an audio signal St from a microphone 111 contained within mouthpiece 101
of handset unit 1A is supplied through an audio frequency amplifier 112 to
a frequency modulating circuit 113, which outputs a corresponding high
frequency FM signal Su in the upper channel of a selected one of duplex
channels A or B. For this purpose, frequency modulating circuit 113 is
provided with a channel selecting signal CH generated in accordance with
the operation of a channel selector switch 154. Channel selector signal CH
may be used to determine the frequency of a local oscillator signal used
to frequency convert the FM signal to radio frequencies. Signal Su is
supplied through a high frequency amplifier 114 and a band pass filter 115
with a pass band including both upper channels to antenna 100, by which it
is transmitted as a radio frequency wave to base unit 2A over the
communication channel.
Referring now to FIG. 3, signal Su transmitted from handset unit 1A is
received at base unit 2A by antenna 200 and is supplied through a band
pass filter 221 and a high frequency amplifier 222 to a mixing circuit
223. Mixing circuit 223 receives a local oscillation signal from a local
oscillator circuit 224 receiving channel selecting signal CH to frequency
convert the signal Su to an FM intermediate frequency signal. This FM
signal is supplied through an intermediate frequency amplifier 225 to an
FM demodulating circuit 226, wherein it is demodulated to produce audio
signal St. Audio signal St is passed to telephone network line 3a through
an audio frequency amplifier 227 and the signal transmission circuit 230
comprising hybrid circuit 231, and relay circuit 232. Hybrid circuit 231
has solid state components and moving contacts to form a transition
between the electronic receiving system 220 and electromechanical relay
circuit 232. Relay circuit 232 includes a relay of the type to make and
break the connection between base unit 2A and telephone network line 3a,
and a hold relay which in a first position can hold a connection with
telephone network line 3a while disconnecting it from hybrid circuit 231
and auxiliary telephone 4, so that telephone communication with telephone
network line 3a is temporarily interrupted during an intercom operation
while keeping the incoming call available on telephone network line 3a.
This operation is referred to herein as reserving the incoming call. The
hold relay has a second position in which telephone network line 3a is
made available for connection to hybrid circuit 231, auxiliary telephone
4, or both. This operation is referred to as releasing the incoming call.
Auxiliary telephone 4 is thus connectable by relay circuit 232 to telephone
network line 3a to constitute the base loudspeaker/microphone or
electro-audio transducer in the intercom telephone system associated with
base unit 2A.
The transmission of signals from base unit 2A to handset unit 1A will now
be described. When incoming message signals are received from telephone
network line 3a, the audio signal Sr is supplied through relay circuit
232, hybrid circuit 231 and audio frequency amplifier 212 to a frequency
modulating circuit 213, which outputs a corresponding high frequency FM
signal Sd in the lower channel of the same duplex channel (A or B) as
signal Su. Frequency modulating circuit 213 is supplied with channel
selecting signal CH for this purpose. Signal Sd is supplied through a high
frequency amplifier 214 and a band pass filter 215 with a pass band
including the lower channels of both A and B channels to antenna 200, by
which it is transmitted to handset 1A over the communication channel.
Referring back to FIG. 2, signal Sd is received by antenna 100 and is
supplied through a band pass filter 121 with a pass band including both
lower channels and a high frequency amplifier 122 to a mixing circuit 123.
Mixing circuit 123 is supplied with a 1ocal oscillation signal from a
local oscillator circuit 124 receiving channel selecting signal CH, so
that signal Sd is frequency converted to an FM intermediate frequency
signal. This FM signal is supplied through an intermediate frequency
amplifier 125 to an FM demodulating circuit 126, wherein it is demodulated
to the audio signal Sr and supplied through an audio frequency amplifier
127 to an electro-audio transducer or loudspeaker 128 contained within an
earpiece of handset unit 1A.
In accordance with an important aspect of the present invention, handset
unit 1A further contains a control circuit, generally designated by
reference numeral 140 in FIG. 2, and base unit 2A similarly contains a
control circuit, generally indicated by reference numeral 240 in FIG. 3.
These control circuits may each advantageously be comprised in whole or in
great part by a microprocessor or microcomputer, contained on a single
integrated chip. An advantageous example is the MSM-6404 microcomputer IC
manufactured by Oki Electric Industry Co., Ltd. Control circuit 140
includes a central processing unit (CPU) 141, for 4-bit parallel
processing, a read only memory (ROM) 142, which stores control programs
for controlling the operation of CPU 141, a random access memory (RAM) 143
serving as a work and storage area, and an input/output (I/O) port 144.
Similarly in base unit 2A, control circuit 240 includes a CPU 241, a ROM
242, a RAM 243 and an I/O port 244, each performing a function
corresponding to that of the element of control circuit 140 having the
same two final digits in the reference numeral. A detailed description is
given below of the operation and control of these elements, but it should
be understood that a control circuit such as control circuits 140 and 240
may, under the control of an appropriate control program, be designed to
perform different functions at different times and to control the
operation of several elements. At each stage of operation of the control
circuit by the control program, the control circuit may be viewed as a
means for performing a certain function. According to an important aspect
of the present invention, the cordless telephone in the intercom mode is
responsive to detection of an incoming telephone call and subsequent
actuation to establish the telephone mode, and at such time control
circuits 140,240 may be regarded as intercom stop means. Similarly, one of
the telephone and intercom modes of the cordless telephone according to
this invention may be established in response to actuation of certain
keys. At such time, control circuits 140, 240 may be regarded as means for
selectively establishing one of the telephone and intercom modes. In
accordance with another aspect of the present invention, two identifying
codes are compared for identity to establish the communication channel,
and at such time control circuits 140, 240 may be regarded as identity
detecting means. The discussion below will make clear at all times what
functions control circuits 140 and 240 are performing and precisely how
such functions are carried out.
Connected to control circuit 140 for controlling the latter are ten-key
panel 151, a talk switch 152, an intercom key 153, the above-mentioned
channel selector key 154, and a dip switch 155. Ten-key panel 151 has
conventional non-lock push button switches for inputting the telephone
number to be called. Talk switch 152 is a three position change-over
switch used for selecting an operational mode of handset unit 1A. When a
movable contact 152a of talk switch 152 contacts fixed contact O (the OFF
position), the power is turned off to all the elements within handset unit
1A except control circuit 140, to place handset unit 1A in an off mode.
When movable contact 152a contacts fixed contact S (the STANDBY position),
control circuit 140 is placed in a standby mode to await the signal Sd
from base unit 2A. When movable contact 152a contacts fixed contact T (the
TALK position), handset unit 1A is placed in a talk mode and the
communication channel between handset unit 1A and base unit 2A may be
established. Clearly, handset unit 1A must be in the talk mode to allow
cordless telephone 10 to be in the intercom mode, or else the handset
operator could not communicate with the base operator. Indeed, in
accordance with one aspect of the present invention, placing talk button
152 in the STANDBY or OFF position when cordless telephone 10 is in the
intercom mode and an incoming telephone call is present achieves actuation
of the intercom stop means thus constituted by control circuits 140, 240.
Channel selector key 154 is a non-lock push button switch for selecting
either channel A or B for the communication channel between handset unit
1A and base unit 2A. This signal specifies the desired upper or lower
channel by specifying the frequency dividing ratio of a variable frequency
dividing circuit contained within local oscillator circuit 124. Dip switch
155 may be an IC with pins selectively set by the operator to enter
respective binary values and is used by the operator to input a selected
identifying code ID to control circuit 140.
Intercom key 153 provides an easily operated intercom start capability
which is very convenient for the operator. Intercom key 153 is a non-lock
push button switch, and a detailed description of its function will be
given below in connection with FIGS. 4 and 5. The respective outputs from
the push button switches forming ten-key panel 151, talk switch 152,
intercom key 153, channel selector key 154 and dip switch 155 are supplied
to control circuit 140 for processing.
As mentioned above, the cordless telephone according to the present
invention may be changed-over to any one of a plurality of modes and the
physical connections therefor are as follows. In the telephone mode, hold
relay 232 releases the incoming telephone call and either the
loudspeaker/microphone of base unit 2A, that is, auxiliary telephone 4, or
the electro-audio transducer of handset unit 1A, which is constituted by
microphone 111 and loudspeaker 128, is placed in communication with
telephone network line 3a. The connection between auxiliary telephone 4
and telephone network line 3a is accomplished directly through relay
circuit 232. In such case, auxiliary telephone 4 is in telephonic
communication with telephone network line 3a. The connection between the
electro-audio transducer of handset unit 1IA and the telephone network
line 3a is accomplished through transmission system 110 and receiving
system 120 of handset unit 1A, transmission system 210 and receiving
system 220 of base unit 2A and connecting circuit 230 including hybrid
circuit 231 and relay circuit 232. In such case, handset unit 1A is in
communication with base unit 2A, in that signals are transmitted
therebetween over the radio waves, but with respect to telephonic
communication, the handset electro-audio transducer 111,128 may be said to
be in communication with the telephone network line 3a.
The cordless telephone may also be operated in the intercom mode, wherein
the handset electro-audio transducer is in communication with auxiliary
telephone 4 (the base electro-audio transducer) through connecting circuit
230. In the intercom mode, the hold relay within relay circuit 232
reserves the incoming telephone call appearing on telephone network line
3a. Thus, the operators at handset unit 1A and base unit 2A communicate
with each other but not with the third party placing the incoming
telephone call, who has been thus put on hold.
Both handset unit 1A and base unit 2A include actuable enabling means for
enabling communication from the respective electro-audio transducer. In
handset unit 1A, talk button 152 enables communication from handset
electro-audio transducer 111,118 when it is moved to its TALK position to
produce an enable signal to place handset unit 1A in the talk mode.
Conversely, when talk button 152 is, placed in either its STANDBY position
or its OFF position, it produces a disable signal at terminal S or T,
which in turn is conveyed to control circuit 140. When in the intercom
mode, control circuit 140 is responsive to the disable signal to end the
intercom mode, and so talk button 152 and control circuit 140 may be
regarded as a handset component of an intercom stop means. The STANDBY and
OFF positions of talk button 152 may collectively be regarded as an
actuated position for stopping the intercom mode.
When receiver 4b is lifted from its cradle, communication is enabled. When
receiver 4b is returned to its cradle, communication is disabled.
Conventionally, this is accomplished by a relay circuit within auxiliary
telephone 4, which itself may be regarded as the transmitter of a signal
when receiver 4b is hung up. When in the intercom mode, control circuit
240 is responsive to the disable signal to end the intercom mode, and thus
receiver 4b and control circuit 240 may be regarded a base component of
the intercom stop means. Receiver 4b mounted on its cradle may be regarded
as in an actuated position for stopping the intercom mode.
An MSK (minimum shift key) modulating circuit 161 is connected to control
circuit 140 for converting binary signals supplied thereto by control
circuit 140 to an MSK signal Sm in the audio frequency band. These binary
signals include identifying code ID, which will be described in greater
detail later, and a dial signal DS corresponding to the telephone number
entered through ten-key panel 151. Importantly, MSK signal Sm may also
include control signals, for indicating to base unit 2A that talk button
152 has been moved or that intercom key 153 has been depressed. MSK signal
Sm is supplied to audio frequency amplifier 112 for transmission to base
unit 2A within signal Sd in the manner described above. The output of FM
demodulating circuit 126 is also supplied to a reception detecting circuit
162 for detecting the presence or absence of signal Sd in the output. As
is well known, the frequency components of the output are different in the
presence or absence of signal Sd. A detection signal NSQ generated by
reception detecting circuit 162 when signal Sd is present is supplied to
control circuit 140.
Base unit 2A contains a similar MSK modulating circuit 261 for encoding the
identifying code ID, channel selecting signal CH, appropriate control
signals, and other signals in a signal Sm transmitted from base unit 2A to
handset unit 1A. In handset unit 1A, an MSK demodulating circuit 163 is
supplied with the output of FM demodulating circuit 126 to demodulate the
identifying code ID, control signals and other signals encoded in MSK
signal Sm. The demodulated signals are supplied to control circuit 140.
According to an important aspect of the present invention, when an incoming
call is detected in base unit 2A and signal Sd is transmitted to handset
unit 1A, signal NSQ is supplied to control circuit 140 and an appropriate
control signal is supplied to a call tone generator 164 for generating a
bell sound signal. The bell sound signal is supplied to audio amplifier
127 causing it to generate a bell sound, i.e. handset unit 1A rings. The
bell sound signal may be generated when handset unit 1A is in the standby
mode or when it is in the talk mode with cordless telephone 10 in the
intercom mode, i.e. in a talk/intercom mode. In a talk/telephone mode, the
handset operator is talking to an outside caller already, while in a
standby/telephone mode, handset unit 1A is in the standby mode and the
base operator is talking to the outside caller, i.e. cordless telephone 10
is in the telephone mode here also.
In the intercom mode the handset operator is holding handset unit 1A with
its microphone close to his ear. In accordance with an aspect of the
present invention, the bell sound at handset unit 1A is produced at a low
volume in the talk/intercom mode to avoid producing a painfully loud sound
directly in the operator's ear. In accordance with another aspect of the
present invention, the bell sounds at both base unit unit 2A and handset
unit 1A cease when the telephone mode is subsequently established.
Control circuit 140 of handset unit 1A generates a control signal TX
supplied to frequency modulating circuit 113 to control whether or not FM
signal Su is output therefrom. As de | | |
