 |
Description  |
|
|
BACKGROUND OF THE INVENTION
The present invention relates to a sound volume controlling apparatus
suitable for use in telephone systems or audio systems, and more
specifically to a sound volume controlling apparatus provided with sound
volume controlling keys for increasing or decreasing sound volume when
depressed.
A sound volume controlling apparatus incorporated in a telephone set to
which receives speech sound or a ringing sound includes sound volume "UP"
and "DOWN" keys. In the above-mentioned apparatus, whenever the "UP" key
is depressed, sound volume increases stepwise, beginning from the key
depression moment, at a constant rate as shown in FIG. 1. On the other
hand, whenever the "DOWN" key is depressed, sound volume decreases
stepwise, beginning from the key depression moment, at the constant rate.
A problem exists in the above-mentioned apparatus, however, because sound
volume starts to increase or decrease the instant that the "UP" or "DOWN"
key is depressed, even when the user or something touches these keys
erroneously. Thus, even if erroneously depressed, the sound volume keys
cause the sound volume inevitably change.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to provide a sound volume
controlling apparatus which can prevent sound volume from being changed
when the user or something erroneously touches sound volume controlling
keys.
To achieve the above-mentioned object, the present invention provides a
sound volume controlling apparatus, comprising: key means operable
manually; time period detecting means coupled to the key means, for
detecting the time period from when duration of operation of the key means
reaches a predetermined time to when the continuous operation of the key
means ends; sound volume value deciding means coupled to the time period
detecting means, for changing sound volume value during the time duration
detected by the time period detecting means; and deciding means, for
changing the sound volume in accordance with the sound volume value
decided by the sound volume value deciding means.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graphical representation for assistance in explaining the prior
art sound volume control;
FIG. 2 (including FIGS. 2A and 2B) is a block diagram showing the entire
embodiment of the present invention is incorporated;
FIG. 3 is a plan view showing a front panel of the key telephone set used
for the system shown in FIG. 2;
FIG. 4 (including FIGS. 4A and 4B) is a circuit diagram showing a sound
volume control circuit incorporated in the key telephone set used for the
system shown in FIG. 2;
FIG. 5 is a graphical representation for assistance in explaining the
operation of an integration circuit and a Schmitt circuit included in the
control circuit shown in FIG. 4;
FIG. 6 is a graphical representation for assistance in explaining the sound
volume control of the control circuit shown in FIG. 4;
FIG. 7 (including FIGS. 7A and 7B) is a block diagram showing the entire
configuration of a key telephone system, in which a second embodiment of
the present invention is incorporated;
FIG. 8 is a diagram showing tables provided in a RAM of the central control
circuit in a key service unit incorporated in the system shown in FIG. 7;
FIG. 9 (including FIGS. 9A and 9B) is a flowchart for assistance in
explaining the sound volume controlling procedure of the central control
circuit in the key service unit of the system shown in FIG. 7;
FIG. 10 is a diagram showing additional tables provided in a RAM of the
second embodiment of the central control circuit in the key service unit
of the system shown in FIG. 7;
FIG. 11 (including FIGS. 11A and 11B) is a flowchart for assistance in
explaining the sound volume controlling procedure of a modification of the
central control circuit;
FIG. 12 is a flowchart for assistance in explaining the setting procedure
of sound volume increase/decrease rate in the modification of the central
control circuit; and
FIG. 13 (including FIGS. 13A and 13B) is a flowchart for assistance in
explaining the sound volume controlling procedure of another modification
of the central control circuit of the present invention incorporated in
the system shown in FIG. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the present invention will be described hereafter with
respect to its application to extension telephone sets in a key telephone
system, in order to control received speech sound volume and ringing sound
volume.
FIG. 2 (including FIGS. 2A and 2B) is a block diagram showing the entire
configuration of a key telephone system. As shown, the key telephone
system generally includes a key service unit 11 and a plurality of key
telephone sets 22 and 23 (only two sets are shown) connected to the key
service unit 11. Further, these telephone sets 22 and 23 include "UP" keys
42 and 54 and "DOWN" keys 43 and 55, respectively to control received
speech sound volume and ringing sound volume.
The key service unit 11 is composed of an office line interface unit 6
connected to an office line 1; key telephone set interface units 8 and 10
connected to the key telephone sets 22 and 23, respectively; a time switch
7; and a central control circuit 9 for controlling the office line
interface unit 6, the time switch 7, and the key telephone set interface
units 8 and 10, respectively.
The above construction will be described hereinbelow in further detail. The
office line interface unit 6 is provided to connect the key service unit
11 to the office line 1, and includes an office line interface circuit 33,
a transformer 34, hybrid coil (2-4 wire switching) circuit 2, a receiving
amplifier 3, a transmitting amplifier 4, a codec 5, and a control circuit.
The office line interface circuit 33 detects an incoming call from the
office line 1, opens/closes a dc loop of the office line, and transmits
numerical signals under control of the control circuit 35. The transformer
34 is provided to couple the office line interface circuit 33 to the
hybrid coil circuit 2.
The hybrid coil circuit 2 receives analog speech signals given from the
office line interface circuit 33 via the transformer 34, and outputs the
received speech signals to the receiving amplifier 3. Further, the hybrid
coil circuit 2 receives analog speech signals outputted by the
transmitting amplifier 4, and transmits the received speech signals to the
office line interface circuit 33 via the transformer 34.
The receiving amplifier 3 amplifies the analog speech signals given by the
2-4 wire switching circuit 2, and outputs the amplified signals to the
codec 5. On the other hand, the transmitting amplifier 4 amplifies the
analog speech signals outputted by the codec 5, and outputs the amplified
signals to the 2-4 wire switching circuit 2.
The codec 5 converts the analog speech signals received from the receiving
amplifier 3 to digital PCM data, and applies the converted PCM speech data
to the time switch 7 via a time division channel allocated to the PCM
speech data. Further, the codec 5 receives the PCM speech data outputted
from the time switch 7 via the time division channel allocated thereto,
converts the PCM speech data to analog speech data, and outputs the
converted speech data to the transmitting amplifier 4.
The control circuit 35 controls the operation (e.g. transmission of
numerical signals, open/close of a dc loop, etc.) of the office line
interface circuit 33 in response to control data given by the central
control circuit 9. Further, the control circuit 35 receives the detection
signals (e.g. incoming call detection signal, polarity inversion detection
signal, etc.) given by the office line interface circuit 33 and transmits
control data corresponding thereto to the central control circuit 9.
The time switch 7 realizes the time division exchange between the inputted
PCM speech data and the outputted PCM speech data. The key telephone set
interface units 8 and 10 receive PCM data outputted from the time switch 7
via the time division channels allocated thereto and control data supplied
from the central control circuit 9, and transmit these received data to
the key telephone sets 22 and 23, respectively in accordance with
ping-pong (digital) transmission method. Further, the key telephone set
interface units 8 and 10 receive PCM speech data and control data
transmitted from the key telephone sets 22 and 23, and transmit the PCM
speech data to the time switch 7 via the allocated time division channels
and the control data to the central control circuit 9, respectively.
The central control circuit 9 is provided with a microcomputer including a
CPU, ROM, and RAM (all not shown). Programs, fixed data, etc. are loaded
on the ROM to operate the CPU. Further, the RAM is provided with memory
areas for storing the current data indicative of received speech sound
volumes and ringing sound volumes of the respective key telephone sets 22
and 23.
The CPU executes various known system controlling operations (e.g. ringing
and switching processing) in accordance with control programs stored in
the ROM. Further, the CPU executes sound volume control processing for the
respective key telephone sets 22 and 23 in accordance with the control
programs.
The key telephone sets 22 and 23 will be described hereafter with reference
primarily to FIG. 2B. Since both the sets are the same in construction,
only the key telephone set 22 is explained. The key telephone set 22
includes a ping-pong transmission circuit 12. The ping-pong transmission
circuit 12 receives PCM speech data and control data transmitted from the
key telephone set interface unit 8 of the key service unit 11 in
accordance with the ping-pong transmission method, and transmits the PCM
signals to the codec 13 and the control data to the control circuit 18.
Further, the ping-pong transmission circuit 12 transmits PCM speech data
outputted from the codec 13 and control data outputted from the control
circuit 18 to the key telephone set interface unit 8.
The codec 13 receives PCM speech data outputted from the ping-pong
transmission circuit 12 and converts the received data into analog speech
signals. The converted analog speech signals are selectively inputted to
either one of an electric sound volume adjusting circuit 45 or 46 by a
handset/speaker change-over switch 44. When inputted to the electric sound
volume adjusting circuit 45, the speech signals are transmitted to a
telephone receiver 15 via a receiving amplifier 14. Further, when inputted
to the electronic sound volume adjusting circuit 46, the speech signals
are transmitted to a speaker 48 via an amplifier 47.
The codec 13 receives analog speech signals outputted from a telephone
transmitter 16 via a transmitting amplifier 17, converts these signals
into PCM speech data, and outputs these digital signals to the ping-pong
transmission circuit 12.
To the control circuit 18, an extension set selecting switch 19, an office
line selecting switch 20, a dial key pad 21 and a ringing sound generating
circuit 36 are connected.
The extension set selecting switch 19 is used when the key telephone set 22
originates a call to another key telephone set. When this extension set
selecting switch 19 is depressed, an extension set selecting data is
outputted from the control circuit 18 and transmitted to the key service
unit 11. The office line selecting switches 20 are used when originating a
call to an office line 1. When any office line selecting switch 20 is
depressed, an office line selecting data is outputted from the control
circuit 18 and transmitted to the key service unit 11.
The dial key pad 21 is used to generate numerical signals for originating a
call. When any numerical key in the pad 21 is depressed, a numerical
signal is formed by the control circuit 18 and transmitted to the key
service unit 11.
When the control circuit 18 receives an incoming call data from the key
service unit 11, the ringing sound generating circuit 36 is driven by the
control circuit 18 to generate a ringing sound. The generated ringing
sound is transmitted to the speaker 48 via the electronic sound volume
adjusting circuit 46 and the amplifier 47.
As shown in FIG. 3, a handset/speaker selecting key 41, a sound volume "UP"
key 42, a sound volume "DOWN" key 43 and a reset key 61 are arranged on
the front panel of the key telephone set 22, in addition to the
above-mentioned extension set selecting switch 19, the office line
selecting switches 20 and the dial key pad 21. In addition, a message key,
a meeting key, a redial key, and a suspension key (the description of
these key functions being omitted herein) are arranged on the front panel.
With reference to FIG. 2 again, the handset/speaker selecting switch 41 is
used for switching the afore-mentioned handset/speaker change-over switch
44. This selecting key 41 is also used to switch an output change-over
switch 39g (shown in FIG. 4A) provided in a command signal circuit 39.
The "UP" key 42 and the "DOWN" key 43 are both connected to input terminals
of the command signal circuit 39. This "UP" key 42 is depressed to
increase the sound volume of received speech sound or ringing sound. On
the other hand, the "DOWN" key 43 is depressed to decrease the sound
volume. These "UP" and "DOWN" keys are also connected to signal processing
circuits 37 and 38 on the handset and speaker side. As described later,
the signal processing circuits 37 and 38 are provided with a shift
register which functions as an up/down counter, respectively.
These "UP" and "DOWN" keys 42 and 43 are used to set the shift register to
up and down count modes, respectively.
In the command signal circuit 39, the input terminals thereof are connected
to the "UP" and "DOWN" keys 42 and 43, and the output terminal thereof is
selectively connected to either one input terminal of a handset side
signal processing circuit 37 or a speaker side signal processing circuit
38 via the afore-mentioned output change-over switch 39g (shown in FIG.
4A). The command signal circuit 39 generates command signals for
increasing and decreasing sound volume in response to the depression of
the "UP" and "DOWN" keys 42 and 43, and outputs the command signals to the
handset side or speaker side signal processing circuit 37 or 38. In this
case, when the depression time of the "UP" or "DOWN" key 42 or 43 is less
than a predetermined time (e.g. 0.5 sec), the command signal circuit 39
will not generate the above-mentioned command signals.
The handset and speaker side signal processing circuits 37 and 38 are the
same in the inner configuration. The signal processing circuit 37 or 38
controls the sound volume value in response to the command signals given
from the command signal circuit 39 to increase and decrease the sound
volume, and outputs the controlled sound volume value to the electronic
sound volume adjusting circuit 45 or 46 and the control circuit 18.
The electronic sound volume adjusting circuit 45 serves to adjust the sound
volume of speech signals outputted from the telephone receiver 15. The
electronic sound volume adjusting circuit 46 serves to adjust the sound
volume of ringing signal or received speech signals outputted from the
speaker 48. The electronic sound volume adjusting circuits can adjust
sound volume to two mutually different values.
FIG. 4 (Including FIGS. 4A and 4B) is block diagram showing the internal
configurations of the command signal circuit 39, the handset side signal
processing circuit 37 and the electronic sound volume adjusting circuit 45
provided in the key telephone set 22. As already described, the handset
and speaker side signal processing circuits 37 and 38 are the same in the
internal configuration. Further, the electronic sound volume adjusting
circuits 45 and 46 (FIG. 2B) are the same in the internal configuration.
Therefore, it is possible to understand the configuration of the speaker
side signal processing circuit 38 and the electronic sound volume
adjusting circuit 46, with reference to FIG. 4.
In FIG. 4A, the command signal circuit 39 is provided with an integration
circuit 39h, a Schmitt trigger circuit 39d, a clock pulse generating
circuit 39e an AND circuit 39f and an output change-over switch 39d. In
FIG. 4B the handset side signal processing circuit 37 is provided with a
shift register 37a, and a latch circuit 37b. The electronic sound volume
adjusting circuit is a resistor ladder circuit composed of a
series-connected resistors 45a, 45b, 45c, 45d, 45e, 45f, 45g and 45h and
analog switches 45i, 45j, 45k, 45l, 45m, 45n, 45o and 45p connected to the
resistors, respectively.
These circuits will be described in more detail hereafter. In the command
signal circuit 39, when the "UP" or "DOWN" key is being depressed, since a
supply voltage (V.sub.cc) side contact of the switch 39g is closed, a
logical "H" level voltage signal is applied to the integration circuit
39h. The integration circuit 39h is composed of a resistor 39b, a
capacitor 39c and a diode 39a. The applied voltage signal is integrated in
accordance with a time constant determined by the values of the resistor
39 and the capacitor 39c and then applied connected to the integration
circuit 39h with the anode 39h and with the cathode thereof connected to
the input terminal thereof.
When the "UP" or "DOWN" key 42 or 43 is released from depression, the diode
39a discharges the electric charge stored in the capacitor 39c in a short
time. The waveform of the output signal of the integration circuit 39h is
shown in FIG. 5A.
The Schmitt trigger circuit 39d forms a square pulse signal as shown in
FIG. 5B in response to the signal outputted from the integration circuit
39h as shown in FIG. 5A. The formed square pulse signal is applied to one
input terminal of the AND circuit 39f.
Here, when the time during which the key is depressed is shorter than a
delay time determined in dependence upon the time constant of the
integration circuit 39h and the turn-on threshold level of the Schmitt
trigger circuit 39d, the Schmitt trigger circuit 39d is not turned on.
Only when the key depression time is longer than the above delay time, is
the Schmitt trigger circuit 39d turned on to apply a square pulse signal
to the AND circuit 39f. The above-mentioned delay time duration can be
determined by selecting the values of the resistor 39b and the capacitor
39c of the integration circuit 39h and the turn-on threshold value of the
Schmitt trigger circuit 39d. Owing to this delay time, the sound volume
control function will not be effected, in case the user touches the "UP"
and "DOWN" keys, erroneously. It may be appropriate to determine this
delay time 1 sec or less (e.g. 0.25 to 0.5 sec) from the practical
standpoint.
When the square pulse signal is being applied from the Schmitt trigger
circuit 39d to the AND circuit 39f, the AND circuit 39f passes a clock
pulse signal from the clock pulse generating circuit 39e to apply it to a
clock terminal of the shift register 37a. Since the clock pulse generating
circuit 39e is so designed that the period of the clock pulse signal is
adjustable, it is possible to adjust the change rate of the resistance
value of the electronic sound volume adjusting circuit 45. By adjusting
the change rate of the resistance value of the electronic sound volume
adjusting circuit 45 according to the types of the telephone transmitter
(e.g. carbon microphone, dynamic microphone, etc.), the difference in the
input-output characteristics of speech signals between various
transmitters can be compensated for, in such a way that the gain of the
receiving amplifier 14 or the gain of the speaker amplifier 47 can be
changed substantially linearly.
The output change-over switch 39g selectively connects the output terminal
of the AND circuit 39f to one of the handset side signal processing
circuit 37 and the speaker side signal processing circuit 38 in accordance
with the depression of the handset/speaker select key 41.
The shift register 37a of 8 stages shifts a logical "H" level signal held
at any one of the stages to the succeeding stage whenever the clock pulse
signal from the AND circuit 39f is applied to the clock input terminal of
the shift register 37a. The output terminals of the 8 stages are connected
to data input terminals of the latch circuit 37b, respectively. Since the
shift register 37a is provided with a function as an UP/DOWN counter,
when the "UP" key 42 is depressed, a mode setting signal of logical "H"
level is applied to the shift register 37a, so that the shift register 37a
is set to an UP count mode. In this UP count mode, the held logical "H"
level signal is shifted in the upward direction shown in FIG. 4 in
response to the clock pulse signals from the AND circuit 39f. When the
"DOWN" key 43 is depressed, a mode setting signal of logical "L" level is
applied to the shift register 37a, so that the shift register 37a is set
to a DOWN count mode. In this DOWN count mode, the held logical "H" level
signal is shifted in the downward direction shown in FIG. 4 in response to
the clock pulse signals from the AND circuit 39f. The number of shifted
stages is determined by the number of the clock pulse signals (the number
of leading edges thereof) outputted by the clock pulse generating circuit
39e within a time period of the square wave signal outputted from the
Schmitt trigger circuit 39d.
This shift register 37a can be reset to the initial condition in response
to a reset signal applied from the reset key 61 arranged in the front
panel of the key telephone set 22. In the initial condition, the logical
"H" level signal is held at the middle stage (corresponding to the analog
switch 45l) of the shift register 37a.
The latch circuit 37b is connected to the shift register 37a in such a way
that the input terminals of the latch circuit are connected to the 8
stages of the shift register via 8 signal wires. Further, the latch
circuit 37b is connected to the 8 analog switches 45i to 45p via 8 signal
wires, respectively. Further, the latch circuit 18 is also connected to
the control circuit 18 (shown in FIG. 2). The latch circuit 37b latches a
signal held at one of the 8 stages of the shift register 37a and outputs
the held signal to one of the 8 analog switches 45i to 45p and the control
circuit 18.
The control circuit 18 recognizes the sound volume value of received speech
signals outputted from the receiving amplifier 14 by discriminating the
"H" level bit position of the signals applied from the latch circuit 37b.
The recognized sound volume value is given to the centrol control circuit
9 of the key service unit 11 through the already-mentioned route and
stored in the RAM of the central control circuit 9.
Each of the analog switches 45i to 45p of the electronic sound volume
adjusting circuit 45 becomes conductive when the logical "H" level signal
is applied thereto from the latch circuit 37b. That is, when the logical
"H" level signal is held at the first stage of the latch circuit 37b,
since the analog switch 45i is conductive, the resistance value of the
electronic sound volume adjusting circuit is determined by only the
resistor 45a, so that the gain of the receiving amplifier 14 (the sound
volume value of the received speech signals) is the maximum. In contrast
with this, when the logical "H" level signal is held at the last stage of
the latch circuit 37b, since the analog switch 45p is conductive, the
resistance value of the electronic sound volume adjusting circuit 45 is a
sum total of the resistors 45a, 45b, 45c, 45d, 45e, 45f, 45g and 45h, so
that the gain of the receiving amplifier 14 (the sound volume value of
received speech signals) is the minimum. As described above, it is
possible to control the sound volume value of received speech signals by
changing the analog switches 45i to 45p allowed to be conductive.
FIG. 6 shows a change in the sound volume when the "UP" key 42 is depressed
under the condition that the resistance value of the electronic sound
volume adjusting circuit 45 is set to the maximum value (the minimum sound
volume value). Here, the period of the clock pulse generated by the clock
pulse generating circuit 39e is 0.5 sec. When the key depression time is
0.5 sec or less, since the Schmitt trigger circuit 39d is not turned on,
the sound volume will not change. However, when the key depression time is
0.5 sec or more, as long as the key is kept depressed, the sound volume
value increases stepwise for each 0.5 sec.
In case the user touches the "UP" or "DOWN" key 42 or 43 erroneously or an
object is brought into contact with the key, since such an erroneous key
depression time as described above is usually 0.5 sec or less, the sound
volume will not change by the erroneous key depression.
A second embodiment of the present invention will be described hereafter.
In this embodiment, in the key telephone system as shown in FIG. 7, the
central control circuit 9 of the key service unit controls the sound
volume of the respective key telephone sets.
In FIG. 7 (including FIGS. 7A and 7B), the respective key telephone sets
22' and 23' are the same in circuit configuration. In the key telephone
set 22', for instance, the selection key 41, the "UP" key 42, the "DOWN"
key 43 and the reset key 61 are connected to the control circuit 18'. The
control circuit 18' detects the depressions of these keys, and transmits
the detected data to the central control circuit 9 of the key service unit
11. Further, the control circuit 18' is connected to the electronic sound
volume adjusting circuits 45 and 46. The resistance value of each of these
adjusting circuits is adjusted in accordance with the sound volume data
given by the central control circuit 9 of the key service unit 11.
Memory areas as shown in FIG. 8 are set in the RAM in the central control
circuit 9. The central control circuit 9 executes the processing as shown
in FIG. 9.
In the RAM, there are provided a key area, a 0.5 sec timer area, and an
output area as shown in FIG. 8. Each of the above-mentioned areas is
divided into plural subareas corresponding to the respective key telephone
sets. In the key area, a code "01H" is stored when the "UP" key is
depressed in each key telephone set; a code "02H" is stored when "DOWN"
key is depressed; and a code "00H" is stored when neither of the keys is
depressed. In the 0.5 sec timer area, a time count value of 5 is set the
instant that "UP" or "DOWN" key of each key telephone set is depressed.
This time count value is decremented one by one whenever 0.1 sec has
elapsed as long as the key is kept depressed. Therefore, when the key
depression time reaches 0.5 sec, the time count value reaches "0" (time
out). In the output area, the sound volume data obtained immediately after
the 0.5 timer area is timed out is stored. Further, when the key
depression is released before the 0.5 timer area is timed out, the sound
volume data obtained immediately after the key is released is stored. The
sound volume data of each key telephone set is read out of the output area
and then transferred to the control circuit of each key telephone set.
FIG. 9 (including FIGS. 9A and 9B) is a flowchart showing the operation of
the central control circuit 9 executed when the "UP" or "DOWN" key is
depressed. The flowchart shown in FIG. 9 will be described by taking the
case of controlling the sound volume of the key telephone set 22'.
When the "UP" key 42 is depressed in the key telephone set 22', the control
circuit 18' transmits the "UP" key depression data to the CPU of the
central control circuit 9 (in step 101). In response to the "UP " key
depression data, the CPU sets "5" to the 0.5 sec timer area of the RAM
(shown in FIG. 8) (in step 102) and additionally "01H" to the key area (in
step 103). Thereafter, when the depression of the "UP" key 42 is released
before the elapse of 0.5 sec (in step 104), the CPU sets "0" as the count
value of the 0.5 sec timer area in the RAM (in step 105) and further "00H"
to the key area of the RAM (in step 106). At this time, the timer area is
stopped from being decremented.
In step 104, when the depression time of the "UP" key 42 reaches 0.5 sec,
the CPU proceeds to step 109. The CPU commands the control circuit 18' of
the key telephone set 22' to check whether the sound volume value of the
electronic sound volume adjusting circuit 45 (or 46) is the maximum (in
step 109). If the sound volume value is not the maximum, the CPU commands
the control circuit 18 to increment one step (a constant value) of the
sound volume value of the electronic sound volume adjusting circuit 45 (or
46) (in step 110). Thereafter, the CPU checks whether the "UP" key 42 is
being depressed (in step 111). If still kept depressed, the CPU sets "5"
as the count value of the timer area (in step 112) and decrements the
count value one by one for each one sec (in step 107). When the count
value reaches zero; that is, if 0.5 sec has elapsed, the CPU proceeds to
step 109 again. While the "UP" key 42 is kept depressed, the above steps
107 to 112 are repeated. As a result, the sound volume is increased in
stepwise fashion as shown in FIG. 6.
This sound volume increment operation ends when the sound volume value of
the electronic sound volume adjusting circuit 45 (or 46) reaches the
maximum or when the depression of the "UP" key 42 is released. Upon the
completion of this sound volume increment operation, the current sound
volume value of the electronic sound volume adjusting circuit 45 (or 46)
determined in step 110 is stored in the output area of the RAM (in step
113).
When the "DOWN" key 43 is depressed, the sound volume is decreased in
stepwise fashion in the procedure similar to the case where the "UP" key
is depressed (as already described) (in steps 114 to 125). In this case,
if the depression time of the "DOWN" key is 0.5 sec or less, the operation
of decreasing the sound volume will not start (in step 117).
In the above-mentioned embodiment, although a count value of "5" has been
set to the timer area of the RAM in order to determine the delay time of
0.5 sec, it is of course possible to select any different count values in
order to determine any different delay times.
A modification of the present invention applied to the key telephone system
shown in FIG. 7 will be described hereinbelow.
In this modification, the speed at which the sound volume is increased or
decreased can be changed according to the user's preference.
A constant area as shown in FIG. 10 is provided for the RAM in the central
control circuit 9 of the key service unit 11, in addition to the areas as
shown in FIG. 8. This constant area is divided into plural subareas
corresponding to the respective key telephone sets. In the respective
subareas, constants indicative of the respective sound volume values to be
increased or decreased for each step are stored so as to correspond to the
key telephone sets, respectively
FIG. 11 (including FIGS. 11A and 11B) shows a flowchart for assistance in
explaining the procedure of controlling sound volume by the central
control circuit 9 in this modification. This flowchart shown in FIG. 11 is
the same as that shown in FIG. 9, except for steps 130 and 131 at which
the sound volume is increased or decreased. In step 130 (or step 131), a
new sound volume value is determined by adding (or subtracting) a constant
read from the constant area shown in FIG. 10 to (or from) the current
sound volume value, so that the sound volume value is increased or
decreased stepwise on the basis of a constant stored in the constant area
according to the user's preference.
FIG. 12 is a flowchart showing the procedure of the central control circuit
9 to rewrite the constant stored in the constant area shown in FIG. 10.
This procedure starts in response to a control data generated when the
user depresses a predetermined combination of keys in any one of the key
telephone sets.
The CPU first checks whether the least significant figure of the received
control data is less than a predetermined maximum number (in step 140). If
the checked result is YES, the CPU checks the function selecting number
included in the control data (in step 141). For instance, where "31" is
the function selecting number for setting a step value by which the sound
volume is increased or decreased, if the function selecting number
included in the control data is "31"the CPU proceeds to step 142. In step
142, the CPU checks whether the new constant value included in the control
data matches the constant value already stored in the constant area. If
both match each other, the processing ends. If they do not match, the CPU
writes the new constant value to the constant area in the RAM. As
described above, any constant value (i.e. sound volume increase/decrease
rate) given by the user can be stored in the constant area, and thereafter
the sound volume is increased or decreased in accordance with the rate
determined by the user.
Another modification of the present invention applied to the system shown
in FIG. 7 will be explained hereinbelow. In this modification, the sound
volume can be increased or decreased in accordance with a geometrical
progression, which is preferable to allow the user to feel the change in
sound volume at a constant rate under due consideration of human's
acoustic sense.
In this modification, the constant area as shown in FIG. 10 is provided for
the ROM in the central control circuit 7. A sound volume change ratio
(constants larger than 1 and smaller than 2 is usual) is stored in the
respective subareas of the constant area.
FIG. 13 (including FIGS. 13A and 13B) is a flowchart showing the procedure
of controlling the sound volume by the central control circuit 7 in this
modification. This flowchart is the same as that shown in FIG. 9, except
the steps 150 and 151 at which for sound volume is increased or decreased.
In step 150 (or 151), a new sound volume value is determined by
multiplying a ratio read from the constant area to the current sound
volume value or by dividing the current sound volume by the read ratio.
Since the sound volume is increased or decreased in geometrical
progression, the human acoustic sense feels that sound volume changes at a
constant rate.
In this modification, it is possible to determine a sound volume change
ratio according to the user's preference by executing the processing
procedure as shown in FIG. 12.
* * * * *
|
|
 |
|
 |
Description |
|
