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I claim:
1. A stand-alone switching system for remotely controlling electrically
operated devices or monitoring locations by the use of DTMF code signals
generated by a telephone keypad, said system comprising a telephone line
input for connection to a telephone network, an input interface circuit
connected to said input and having an auto-dialer circuit, a communication
circuit connected between said interface circuit and a microcontroller;
said microcontroller being connected to a switching sub-system for
switching said electrically operated devices and/or an analog control and
monitoring sub-system, all of which perform predetermined functions
implemented by said user through said telephone keypad by using a
programming or command access algorithm through a series of option codes
punched on said keypad, said communication circuit operating in a DTMF or
modulated signals depending on the source of said input signal codes, said
input interface circuit having a digitally filtered ring detector for
discriminating between true telephone rings and undesirable pulse signals,
and a switching device when in a first position connects a telephone ring
detector to said telephone line to receive said true telephone rings and
to connect them to said microcontroller, said microcontroller causing said
switching device to assume a second switch position after said ring
detector has received a predetermined number of rings, feedback signals
being connected through said second switch position to feed back
information to said user, a speech circuit connected to an output of said
second position of said switching device, a modem circuit connected
between said speech circuit and said microcontroller for two-way
communication through modulated signals or a DTMF decoder circuit
connected between said microcontroller and said speech circuit for
receiving and decoding DTMF function code signals as well as frequency
from said speech circuit to feed said microcontroller to execute output or
programming commands or to monitor the status of said electrically
operated devices, said switching sub-system having a plurality of input
and output channels, said output channels being equipped with switches to
switch said electrically operated devices, said input channels being
connected to feedback signalling elements to verify the operation and to
monitor said electrically operated devices which have been switched, said
analog control and monitoring sub-system having a plurality of input and
output channels, said input channels being monitoring channels and
receiving analog signals from a remote industrial device and converting
same to a digital signal, said output channels feeding regulating signals
to industrial actuator devices to be controlled.
2. A switching system as claimed in claim 1 wherein said switching device
is a switching relay circuit.
3. A switching system as claimed in claim 1 wherein an audio circuit for
monitoring an environment is further connected to said speech circuit,
said audio circuit being connected for two-way audio communication with
said speech circuit, said audio circuit having a speaker output and a
microphone input to permit sound communication between a remote location
and said user.
4. A switching system as claimed in claim 3 wherein said audio sub-system
is programmed to enable said two-way audio communication, or to disable
said speaker output only, or to disable said microphone only or to disable
completely said two-way audio communication.
5. A switching system as claimed in claim 1 wherein a speech synthesizer
circuit is connected between said microcontroller and said speed circuit
for transmitting pre-programmed voice messages to said user.
6. A switching system as claimed in claim 5 wherein said speech synthesizer
circuit is an integrated circuit having a ROM memory in which are words
and phrase data which is sent to said microcontroller according to address
codes sent by said microcontroller, said microcontroller transmitting to a
speech synthesizer wherein a vocal signal is transmitted through a filter
to said speech circuit to produce messages to be communicated to said
user.
7. A switching system as claimed in claim 1 wherein a DTMF dialer circuit
is connected between said microcontroller and said speech circuit for
transmitting DTMF or code signals to dial recorded telephone numbers for
automatic message transmission.
8. A switching system as claimed in claim 7 wherein said auto-dialer is
programmed to enable or disable said auto dialing functions.
9. A switching system as claimed in claim 1 wherein a call progress circuit
is connected between said microcontroller and said speech circuit for
monitoring sounds from said telephone line input to instruct said
microcontroller by a binary code is there is no communication established
from an automatically dialed telephone number after a predetermined number
of rings.
10. A switching system as claimed in claim 1 wherein said microcontroller
is provided with an electrically erasable and programmable read only
memory (EEPROM) which is programmed by the user by telephone using DTMF
code signals, and an external read only memory for the storage of data for
a speech synthesizer circuit.
11. A switching system as claimed in claim 10 wherein a plurality of option
codes are stored in said EEPROM, said codes being changeable by said user,
one of said codes being a personal access code to allow access to a
command mode of said EEPROM, a programming master code to provide access
to codes in the EEPROM, a device identification transmission code to
identify a malfunction of a monitored device and ring number code to
determine the number of rings after which the device will pick up the
telephone line and programmed to permit two devices to be connected on
said same line.
12. A switching system as claimed in claim 11 wherein said switching
sub-system includes an application mode option code, an output contact
position code, an auto-off and emergency-off code which permit said system
to instantaneously and permanently disconnected a load if a monitoring
circuit detects stoppage and/or malfunctioning of said load.
13. A switching system as claimed in claims 1 of 12 wherein said output
contacts of said switching sub-system are programmed via the application
mode setting to be:
i) continuous action contacts wherein each said contacts monopolize one
channel,
ii) momentary action pair of said contacts wherein each pair of contacts
monopolize two channels, or
iii) a momentary action simple contact which monopolize one channel.
14. A switching system as claimed in claim 1 wherein said microcontroller
comprises a time clock to pre-program functions of devices associated with
said switching sub-system and analog control and monitoring sub-system,
said time clock being controlled by said telephone keypad.
15. A switching system as claimed in claims 14 or 11 wherein said switching
sub-system includes a time clock setting, and an automatic switching
ON/OFF setting for said time clock.
16. A switching system as claimed in claim 1 wherein said switching device
is a ring detector circuit having a double pole double throw relay which
when in said first position connects said telephone line input to a
resistor-capacitor network to compose an input to a ring detector, a
resistor limits the current of said telephone signal through two parallel
inversely connected diodes, a capacitor between said resistor and diodes
to block the DC component of said telephone signal and letting a 20 Hz AC
signal component through, one of said diodes removing the negative
half-wave of said AC component, the other of said diodes being a light
emitting diode which illuminates when said 20 Hz AC signal component is
present and actuates an opto-coupled transistor to feed said
microcontroller.
17. A switching system as claimed in claim 16 wherein said switching device
further comprises a transistor which energizes the coil of said switching
relay when receiving a validation signal from said microcontroller to
switch to said second position and disconnecting said ring detector
circuit.
18. A switching system as claimed in claim 1 wherein said analog control
and monitoring sub-system includes programming settings which are stored
in said EEPROM, said setting including the following programming
functions:
a) the type of read unit setting,
b) the name of the unit,
c) the bottom scale magnitude setting,
d) the top scale,
e) the centre window reference for regulation setting,
f) the output window delta regulation setting,
g) the decimal scale divider setting,
h) the setting to enable or disable the analog control and monitoring
dependability and inter-relation with the AUTO-OFF supervision function in
the switching sub-system,
i) the setting for the Read and Speach and Regulation sampling rate,
j) the setting to allow shifting of the reference windo, VP or DOWN. |
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Claims |
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Description |
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SUMMARY OF INVENTION
1. Field of the Invention
The present invention relates to an improved method and system for remotely
switching, regulating and monitoring electrically operated devices by the
use of signals generated by a telephone or modem.
2. Description of Prior Art
In my earlier U.S. Pat. No. 4,845,773 issued Jul. 4, 1989, I described a
method and a system for remotely switching an electrically operated
device, such as electrical baseboard heaters, by the use of signals
generated by a telephone. In that particular system, I controlled remote
switches by detecting a specific code of sound signals generated by the
telephone. It was necessary to locate the switching system in close
proximity to a telephone whereby to detect the ringing sound whereby the
switching system could be actuated. With that particular system, I was
more concerned with the control of various electrical devices such as heat
pumps, motors, electric elements, contactors, etc. However, there is a
need to provide an improved system in which it is not necessary to detect
audible sound signals and which has an infinite number of applications and
which is also programmable by the use of DTMF telephone signals or modem
signals.
SUMMARY OF INVENTION
Accordingly, the improved system of the present invention is comprised of a
common telephone input consisting of two wires which are to be connected
to a standard telephone telecommunication network. A 12-volt or 24-volt
power supply and a battery back-up provide the power to the system with
inputs and outputs for three sub-systems. The first is an audio sub-system
and consists of microphones which allows the system to listen to its
environment. The outputs of this sub-system are loudspeakers which permit
the user to communicate with the room on the other end of the line. This
is similar to a "hands free" telephone receiver. The second sub-system is
an "ON/OFF" switching sub-system whose input is the feedback line from the
external switching element (sensor), and the outputs are dry contacts used
to switch electrically operated devices on or off remotely by telephone.
The third sub-system also consists of inputs and outputs and wherein the
inputs represent analog variables (for example a pressure measurement),
and the output is a command signal (for example to a motor or actuator),
which incrementally changes the analog reference which is measured by the
input.
The device allows the remote access to the three sub-systems through the
use of a telephone or a computer and modem. For example, if the user
wishes to speak to, or simply audit the activities in a conference room,
auditorium, classroom, etc., he/she simply communicates with the system,
accesses the audio sub-system and commands either the speak/listen or
simply the listen mode of that system.
For the "ON/OFF" switching sub-system, the user employs a standard DTMF
telephone keypad to switch on or off, or simply confirm the status of an
externally switched electrically operated device.
For the third sub-system, the user remotely gains access to the system,
again by telephone, and may control and/or monitor the status of an analog
variable. A digitally synthesized voice will verbally convey the status of
the variable. The user may also vary the predetermined setting of the
reference for this variable by commanding an incremental change to it. The
user will wait for and receive verbal feedback, via the digitally
synthesized voice, of the status of the changing variable. This
communication may also be performed by computer if the user implements the
"Computer Communication" via a modem.
Therefore, this is a bidirectional system where the user may listen to a
digitally synthesized message, or audit the conversation in a room, or may
remotely switch on or off, or simply change the setting of an analog
variable, all commanded simply with a DTMF telephone keypad.
This is a bidirectional system on the "incoming call" level. The system
also has the capacity, via the "auto-dialer", to call and convey messages,
however, the system is unidirectional in this mode as it is unable to
receive commands. As an example of this mode, the "ON/OFF" switching
sub-system can sense a malfunction in an electrically operated device, for
example, caused by an open or closed pressure switch triggered by an
abnormally high pressure buildup or loss. There is an interruption
requested in the interior of the device which will then send an
auto-dialing code in the system, which proceeds to dial one or more
preprogrammed telephone numbers. A synthesized voice will communicate the
breakdown to the person who answers the telephone call. This "auto-dialer"
function may also be executed through a modem. The system dials the modem
telephone number and sends the computer codes which identify the defective
zone.
We can thereby conclude that this is a simple "STAND ALONE" system, which
is not as complex as the current energy management systems used in large
buildings or industrial security systems. The system of this invention
easily connects with standard electrically operated devices thereby
rendering it universally functional with an infinite number of possible
applications, such as alimentary, agricultural, manufacturing, plastic,
industrial, process control, government institutions and building
management, to name a few. It is pointed out that the three sub-systems
are not exclusively integrated in all system applications.
According to a broad aspect of the present invention, there is provided a
stand-alone switching system for remotely controlling and monitoring
electrically operated devices or monitoring locations by the use of DTMF
code signals generated by a telephone keypad. The system comprises a
telephone line input for connection to a telephone network. An input
interface circuit is connected to the input and has an auto-dialer
circuit. A communication circuit is connected between the interface
circuit and a microcontroller. The microcontroller is connected to a
switching sub-system for switching the electrically operated devices
and/or to an audio circuit for monitoring an environment and/or an analog
control and monitoring sub-system, all of which perform predetermined
functions implemented by the user through the telephone keypad by using a
programming or command access algorithm through a series of option codes
punched on the keypad. The communication circuit operates in a DTMT or
modulated signals mode depending on the source of the input signal codes.
According to a further broad aspect of the present invention, there is
provided a method of effecting a remote function by the use of DTMF code
signals generated by a telephone keypad and representative of a
programming or a command access algorithm. The method comprises providing
a stand-alone switching system. Depressing keys on the keypad to generate
a personal access code signal to permit the system to connect itself to a
telephone line generating the personal access code signal. The access code
signal is analyzed by the system to determine if it is a human command or
a modem command. The system automatically connects a communication circuit
depending on the nature of the access code signal analyzed. A sub-system
is accessed by an access code. The sub-system is comprised of a switching
circuit for switching electrically operated devices, an audio circuit for
monitoring an environment or an analog control and monitoring circuit for
controlling and monitoring a remote process apparatus.
BRIEF DESCRIPTION OF DRAWINGS
A preferred embodiment of the present invention will now be described with
reference to the example thereof as illustrated in the accompanying
drawings in which:
FIG. 1 is a basic block diagram showing the main functions of the system of
the present invention;
FIG. 2 is a detailed block diagram showing the global interconnections
between the different circuits used in the system of the present
invention;
FIG. 3 is a schematic diagram of the telephone network interface with the
system including the circuit of the ring detector;
FIG. 4 is an illustration of the calling signals and pulses vs. the other
undesirable signals to be rejected;
FIG. 5 is an algorithm showing the procedures of the method to reject the
undesirable signals illustrated in FIG. 4;
FIG. 6 is an interconnected block diagram of the integrated circuits used
to process the incoming and outgoing telephone calls;
FIG. 7 is a schematic diagram showing the connections of the MODEM with the
microcontroller and the telephone interface;
FIG. 8 is an interconnecting circuit diagram of the voice synthesizer with
the microcontroller, the voice ROM and the telephone speech interface;
FIG. 9 is a flow chart showing, via incoming calls, the access to remotely
controlling, supervising or programming the system;
FIGS. 10A, 10B and 10C are illustrations showing the locations and codes to
program the options of the system. The codes shown represent the factory
preprogrammed codes;
FIG. 10D is a table showing the switching application attributes of the
output channels when programming the ON/OFF switching sub-system;
FIG. 10E is a schematic ladder diagram showing four different control
circuit applications illustrating the different switching output contact
activation methods and illustrating some examples of supervision feedback
connections for monitoring the ON/OFF switching sub-system;
FIG. 11 is a schematic and interconnecting diagram of the audio sub-system
showing the remote controlled audio elements by telephone via a
microcontroller;
FIG. 12 is a flow chart showing the remote control and monitoring algorithm
of the audio sub-system:
FIG. 13 is a flow chart showing the stay on line and automatic hook-off
algorithm when the system is communicating via the telephone network;
FIG. 14 is a flow chart showing the algorithm to program the options of the
system;
FIG. 15 is a flow chart showing the remote control and supervision of the
ON/OFF switching sub-system;
FIG. 16 is a schematic diagram showing the input channels of the
supervision and the output visual status monitors of the ON/OFF switching
sub-system of the invention;
FIG. 17 is an illustration of the input signals for the supervision of the
ON/OFF switching sub-system;
FIG. 18 is a flow chart of the method used for digitally filtering the AC
supervision signals in the ON/OFF switching sub-system;
FIG. 19 is a schematic diagram showing the output relay drivers controlled
by the microcontroller for the ON/OFF switching sub-system;
FIG. 20 is a flow chart showing the remote monitoring and temporary
shifting of the reference window for regulation of the analog control and
monitoring sub-system;
FIG. 21 is an interconnecting block diagram showing the analog input
interface between an external linear transducer and the A/D converter for
the analog control and monitoring sub-system of the current invention;
FIG. 22 is an interconnecting block diagram showing the output regulation
interface between the microcontroller and the external linear actuator for
the analog control and monitoring sub-system; and
FIG. 23 is a flow chart showing the auto-dialing and call process algorithm
of the system.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to FIG. 1, this block diagram illustrates the general layout
of the system including the three sub-systems. The telephone network 10 is
connected via a simple telephone jack to the system interface 11. This
interface contains an "auto-dialer" which would automatically dial a
telephone number should a functional defect occur. The telephone interface
of the "auto-dialer" is common for the three sub-systems. Reference
numeral 12 represents the user communication with the device by use of a
standard DTMF telephone keypad. This communication is also possible via a
computer 13. The processor 14 is the control center of the system. It
integrates the algorithms and methods implemented. The inputs and outputs
are included in 15, 16 and 17, representing the three sub-systems, the
"audio", the "ON/OF switching" and the "analog control and monitoring
input/output" respectively.
In FIG. 2, a more detailed block diagram for the system is shown. The
various interrelated circuits, the heart of which is the microcontroller
22 is illustrated in this Figure. Numeral 18 denotes the protective filter
which is incorporated on the printed circuit board and is used to
eliminate all transients and surges over the telephone lines, thereby
protecting the system. Numeral 19 denotes a circuit which contains a relay
which can be in either the hook-on or hook-off position. If all is normal,
the relay will be in the hook-off position. When the system answers the
telephone, the relay places itself in the hook-on position. The relay is
constantly monitored by the ring detector 20 when in the hook-off
position. This circuit is used to analyze the pulses from the telephone
rings and will be further explained in FIG. 3. The output 20 goes to the
microcontroller and is analyzed algorithmically. The hook-on/hook-off
relay 19, when in the hook-on position, is connected to a circuit called
the "speech circuit". This circuit adapts the impedance of the telephone
line with the system, via the speech input, all the sounds, signals,
voices, etc., will pass through this wire to the hook-on/hook-off relay
contact. This circuit will be further explained in the discussion of FIG.
6. Note that the arrows in the illustrations indicate inputs and outputs.
For example, at numeral 23, we note the "DTMF dialer", as it receives
orders from the microcontroller, it will send DTMF signals in order to
dial the telephone numbers recorded for automatic message sending to the
outside. Numeral 26 denotes the DTMF decoder used to internally decode
numerical function keyed as well as the frequency from the speech 21, and
once decoded, will send them to the microcontroller which will execute
either output commands or programmed commands, or monitor the status of
electrically operated devices. This is done by the decoded DTMF, as given
by human input. Numeral 26' is an independent DTMF input which is used to
give commands to the microcontroller via a local dual tone generator. The
modem circuit 25 performs the same functions as the DTMF, but rather than,
as in the human case, the commands come from the speech circuit, it is
connected to another external modem which modulates sounds in order to
send digital signals to the microcontroller via output 25'. Numeral 27
denotes the call progress circuit which serves to monitor sounds from the
telephone line in order to alert the microcontroller if there is no
response from an automatically dialed telephone number after a
predetermined number of rings. This circuit will send a code to the
microcontroller by communicating the status of the telephone line at that
given moment. The status refers to the sounds provided by the
telecommunication company in order to communicate a "busy" signal, or
other common sounds including a dead (soundless) telephone line. The call
progress circuit will convey the status via a binary code to the
microcontroller, which will proceed to hook-off or re-dial another number,
etc., as will be later explained in the call progress algorithm. The audio
switching circuit 28 is the audio sub-system 15 of FIG. 1. It is the
sub-system which allows communication with microphone or the loudspeakers
in order to monitor or speak with a room, moreover the sub-system which
permits the connection to the microphone, speaker, etc. Also present are
independent audio-in and audio-out inputs of different impedance which
serve to monitor the sounds originating from audiovisual equipment, along
with an auxiliary input for a local preamplifier rather than a speaker and
microphone. The microcontroller is related to a memory called the EEPROM
29 which is an electrically erasable and programable read-only memory. The
content of this memory will be programmed by the user. We will later
explain the "custom" codes which the user may program by telephone, such
as the access code and the master code which allow reprogramming of the
device, the telephone numbers which the device dials in its automatic
dialing mode, the number of rings after which the unit will answer the
telephone, etc. All this information, along with the setup of the device,
must be programmed in the EEPROM and must be retained even during a power
failure. The external ROM 30 is a read-only memory used to augment the
internal memory of the microcontroller and is devoted to the storage of
the words, phrases and the data used in the digitally synthesized voice
which will be monitored and controlled by the speech synthesizer. Thus,
the microcontroller selects the combination of words which must be used at
a given time and sends this to the speech synthesizer which then sends it
to the speech circuit so that the listener at the other end of the phone
line may hear the message. Therefore, the words, phrases and various codes
are all stored in the form of binary codes in the "external voice ROM".
With reference to 31, 31', 32, 32', 35, 36, 35' and 36', all these numerals
collectively belong to the "ON/OFF" switching sub-system 16 of FIG. 1. In
this description, we are discussing only two input and output channels,
however the dash-line between 31' and 32 represents "n" systems with "n"
possible input and output channels. The output circuits 32 and 32' are
identical. They consist of dry contacts which may be programmed to be
normally open, normally closed, momentary action or continuous action.
These contacts serve to switch an external electrically operated device,
such as a motor contactor, a heating element, lamp or lighting system,
etc. The inputs 31 and 31' are used to verify that the command sent by the
output was properly executed. For example, the switching on of a motor by
the output 32 drives a belt which in turn powers a compressor thereby
increasing the pressure in a tank. The tank contains a pressure switch
which will trip at a given pressure--this switch will also provide a
feedback input 31 and will determine if the pressure is truly built up in
the tank. Therefore, this input serves to supervise the output 32. We will
later see that this feedback not only serves to monitor the output, but
also serves, in the case of a malfunction, to send a signal to the
microcontroller which will proceed to shut off the load 32. The
microcontroller will then access the auto dialer and will communicate the
problem to the user.
The visual indicator No. 1 (35) is a light emitting diode which lights up
if switch 31 is operational. This is to say, if output No. 1 is active V1
lights up, similar to 35' which is for V2, but for output No. 2.
With reference to L1 (36), this is a local momentary action push button
which is used to switch on output No. 1 if pushed once, and to switch it
off if pushed a second time. In other words, L1 and L2 are local commands
used to activate or deactivate the outputs without use of the telephone.
Note that if the unit is in contact with exterior telephone communication,
the operation of these inputs is inhibited. Visual indicator VO ref (33)
is the visual indicator connected to the telephone network, for example a
light, which will be lit if the device is connected to the telephone
network. If the device is not connected to the network, then this light
will remain switched off. This is triggered via the switching element,
which is a common switch LO (34) which is in series with two wires that
provide the telephone connections to the input filter circuit 18. Visual
indicator VO (33) is not only a visual indicator of connection, but as the
telephone rings, it switches on and lights up in unison with the rings of
the telephone allowing one to visualize that someone is contacting the
device. This same visual indicator VO (33) has a third function which is
the visual confirmation of the zeroing of the master code and access code,
described later. This is used in the case of loss of the access code or
master code, which are normally programmed by telephone. Due to their
loss, either through attrition or forgetfulness, then this must be
manually reset by dismantling the device and shorting out two pins on the
printed circuit board. At this point, the system will reset the master
code to 0000000 and the access code to 1111. Visual indicator VO (33) will
blink rapidly in order to indicate the re-setting of the hardware.
With respect to the analog control and monitoring sub-system 17 of FIG. 1,
it consists of blocks 39, 39', 40, 40', 41, 42, 41' and 42'. The input for
circuit 1A (for analog) will later be described in FIG. 22. It is also
shown to consist of input and output channels, but the dash-line between
39' and 40 indicates an infinite number of analog circuits. For the time
being, we will represent them as only two channels; two inputs and two
outputs. Input channel 39 receives the standard analog signal from a
remote source such as an industrial process where we often find
transducers which give 4 to 20 mA signals, or 4 mA on the bottom scale and
20 mA on the top scale. This signal will be interfaced to the
microcontroller via an A/D converter. The output 40 is capable of
incrementally increasing or decreasing the output signal which serves to
regulate the value of the actuator. This actuator may be a motor, a valve,
or a servomechanism, etc.
Also, note that the microcontroller will maintain the output at a given
value or within a specific range. The visual indicator 1A (41) may be a
liquid crystal display which will display the value of the monitored
analog variable. L1A may be employed as a local switch increasing or
decreasing the controlled analog variable, whose output 40 is to be
regulated. Circuits 41' and 42' operate in a similar fashion. Note that
the microcontroller 22 also incorporates a "time clock" function which is
used in the "input/output switching" sub-system giving it the capability
of preprogrammed switching (on and off at predetermined times),
complementing the telephone dispatched command. The features of this
timer, such as its ability to skip Saturdays and Sundays, will be
discussed later. The time clock may be disengaged by programming of the
device, and then activated by telephone communication. The microcontroller
22 manages all the operations of the system, such as switching,
communications, automatic dialing, DTMF decoding, call progress analysis.
It even manages the manner in which the speech synthesizer sends its
messages. The microcontroller is in fact the heart of the system--and all
the methods employed comprise the control software of the microcontroller.
Block 43 represents the power supply and backup battery charger.
FIG. 3 illustrates the telephone input filter 18 of FIG. 2, the switch used
to relay the telephone network to the device, the hook-on/hook-off relay
48 to the opto-coupler used to detect the rings thereby sending this
information to the microcontroller. Numeral 44 represents the tip and ring
connection. Resistor 45 is used as a protective fusible resistor while
varistors 46 are used as voltage attenuators in the case of a power surge,
by producing a voltage drop across 45, and in the case of an extremely
high transient voltage, actually melt the resistor 45, thereby making it
act as a fuse. Therefore, this prevents power surges from passing through
the electronic circuitry. Switch 47 is similar to switch 34 described in
FIG. 2 and is used to switch on and off the system's telephone line, while
at the same time, the two poles serve to inform the microcontroller of its
"ON" and "OFF" position. The double pole, double throw relay "DPDT" 48 in
its rest position connects the telephone line to the resistor-capacitor
network 49, 50, 51 52 which composes the input to the ring detector.
Resistor 49 serves to limit the current through the two diodes 51 and 52.
Capacitor 50 blocks the direct current of the telephone signal while
letting the 20 Hz alternating current component pass through. Diode 51 is
used to remove the negative AC half-wave, while the light emitting diode
52 illuminates with the presence of a 20 Hz frequency. This signal is then
transmitted to the opto-coupled transistor 53 which is then relayed to the
input port of microcontroller 54. This microcontroller will proceed to
analyze, using a procedure which will later be described, the waves sent
through the telephone lines when the telephone rings. When the
microcontroller counts a given number of rings, it will ask the device to
"hook-on". Transistor 55 will receive this signal from the microcontroller
to energize the coil of relay 48, thereby switching the relay contacts to
the hook-on position. In this position, the ring detector circuit is
disconnected from the microcontroller while circuits 56, 57 and 58 will be
connected to the speech circuit. The speech circuit has an impedance in
Ohms required by communication companies, therefore, the line will be
loaded as per this regulated impedance. Diode bridge 57 is present in
order to prevent the reverse polarity of the tip and ring. Zener diode 58
is used to augment the protection already provided by 45 and 46 in case
the voltage exceeds 40 or 50 volts. It will provide protection from sudden
transient surges (voltage spikes). Capacitor 56 eliminates radio
frequencies and filters high frequency noises.
The transistor 59 and light emitting diode 60 are used as visual indicators
and are illustrated in FIG. 2 by block 33. This light emitting diode will
turn on and off as the telephone rings, and will also go off if switch 47
is in the off position, as shown. If this switch is in the ON position,
the telephone network is connected to the device and the light emitting
diode 60 will turn on. This same diode, as previously described, will
blink rapidly if the user resets the access and master codes in the
circuit.
The square waves 62 of a telephone ring are illustrated in FIG. 4. These
are seen at the output of the opto-coupled transistor 53 when the
telephone rings. The envelope of these waves, representing the total time
for a calling pulse and silence, is illustrated in 61.
Alternately, some telephone companies and office telephone system
manufacturers (for internal calls) employ a double ring calling pulse 63.
The 20-cycle sinusoidal ringing signal 64 is similar to the one "seen" by
the opto-coupled transistor. Due to the differences in the calling pulses
generated by different telephone system manufacturers and between one
country and another, the microcontroller has been equipped with a method
of analysis for the calling pulses. There is a switch (on either the
hardware or software) which is always in the off position. However, when
the device is installed by the user, this switch is placed in the on
position, thereby placing the device in the learn mode. The user will then
call from another telephone and let it ring five or six times. The
microcontroller will study the particular calling pulse. The user then
disconnects the device placing the switch in the off position. The system
will have programmed the particular calling pulse pattern within the
EEPROM. The device will then compare calling patterns from incoming calls
to these standards.
The pattern generated by a rotary dial telephone connected on the same line
is shown in 65. When we dial a number on such a telephone, these may be
transmitted to the microcontroller which must discriminate and eliminate
such pulses since they represent nothing. The algorithm which analyzes and
rejects these pulses will later be described. The square waves 66
represent hook-on/hook-off "glitches". These glitch patterns are sensed by
the microcontroller via the opto-coupled transistor. If they do not
conform to the pattern of the telephone rings, they will be eliminated.
The algorithm in FIG. 5 represents the filtering method of these undesired
signals and is used to validate the actual calling pulse.
FIG. 6 illustrates the detailed speech circuit 21 of FIG. 2 with its
inputs, outputs and its interconnections with other blocks. The audio
signal output is accessed at 71 and 68. These two wires are the output of
push/pull amplifier used to drive a speaker. This signal, available
between 68 and 70 is caused by voices from external telephone sounds along
with the signals emanating from an internal microphone 70. The output
audio signal coupled with the input to the DTMF decoder. The sounds coming
from a distant telephone will be decoded. This audio signal is also
coupled with the call progress circuit which serves to analyze the sounds
from an automatic dialing to recognize a busy signal, an unanswered call
or a defective communication. This same audio signal if connected with the
modem circuit input thereby permits the analysis of the modulated signals
coming from an exterior modem connected to the device through telephone
lines. The microphone input to the speech circuit is shown at 70. This
input, as described later, is used to send to an external telephone the
sounds within the room where the device in installed. The DTMF input 69 is
used to send all the sounds other than those picked up by a microphone,
such as the touch tone sounds generated by the device during an auto
dialing call and those sent to the telecommunications company. This DTMF
input is also used by the speech circuit as an input for the voice
generated by the speech synthesizer or by the internal modem. The output
signal of this modem, shown in FIG. 7, is sent to a remote modem. Mute
control 72 is a sound inhibitor towards the output 71 and 68. While the
auto dialer dials a telephone number by pulse or touch tone, the mute
control attenuates the audio output so that these sounds are not processed
by the internal DTMF decoder. These tones are not meant for the device but
for the telephone company which will link the device to an external
telephone. The microcontroller 22 will trigger the automatic dialing by
sending the information to the DTMF dialer via point 73 during an
emergency interruption. This information, or numbers, are stored in the
memory of the EEPROM 29. If the telephone company or this device fail to
understand the DTMF codes, it would be possible, via the microcontroller,
to auto-dial using the pulse mode rather than the DTMF dialer 37, see FIG.
2. The dialing of the telephone numbers will occur with the rapid opening
and closing (10 pulses per second) of the hook-on/hook-off relay. In the
programming of the initial system configuration, the option for pulse or
DTMF dialer is provided for, as will be discussed later. The call progress
circuit receives audio sounds in the input of 68 and contains a binary
output 76 which is made up of three bits. The eight possible combinations
of these three bits will tell the microcontroller the status of the
telephone line. For example, 000 may indicate that the line is functional,
001 may indicate an occupied telephone connection, etc. The valid data
output 77 is used to inform the microcontroller that the data input 76 is
valid and may be accepted. Connections 75 are used as control functions
between the call progress circuit and the microcontroller. The DTMF
decoder 74 is used to decode the tones and frequencies which emanate from
the speech circuit by line 68. These frequencies, generated by the
external telephone keypad, are decoded and the results are transmitted to
the four-bit data bus 78 which gives a possible sixteen combinations for
the numbers on the keypad. The valid data 79 is similar to the function of
77. The DTMF input 80 is an auxiliary input. This input permits the
inputting of local commands or to locally program the microcontroller with
a local DTMF generator without the | | |
