GB1594931A - Telephone operated switching device - Google Patents

Description

(54) TELEPHONE OPERATED SWITCHING DEVICE (71) I, RICHARD JOHN HOWLING, a British subject of 20, Old Coast Guard Road, Sandbanks, Poole, Dorset, BH13 7RL, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a control system for, and a method of, controlling the operation of an electrical appliance in response to a remotely initiated action. More particularly the invention is concerned with a control system responsive to normal signals transmitted to a telephone.

One application for a control system is where it may be desired to switch on the heating equipment in a house or flat in advance of a visit to ensure the rooms are heated on arrival. Another application for the system would be to operate lighting or heating in blocks of flats or other buildings. Generally, simple time switches and thermostats are not flexible enough to cope with the various changes in conditions and requirements which can occur.

According to the invention a control system is provided for controlling the operation of an electrical appliance in response to a sequence of normal calling signals provided to a telephone associated with the system but independent of the appliance as a result of a remotelyinitiated action said system comprising means for providing local digital signals in response to said sequence of normal calling signals, logic means for assessing said local signals to detect whether said local signals indicate a correct pre-settable code imparted by the sequence of calling signals and control means selectively operated by the assessing means to control the appliance, e.g., by actuating switching means connected to switch said appliance on or off. To avoid fraudulent use of the telephone, means can be provided to ensure a chargeable record is made of the use of the system.

The local signals may be generated by an electrical or electromagnetic or an optical device. Conveniently, the means for providing the local signals may include a microphone directly sensitive to the alert terminal signals of the telephone although an inductive coil sensitive to the electrical signals arriving at the telephone can be used. In another construction, a light source is energized when the normal calling signals are received by the telephone and the light source activates a suitable sensor. In general, however the means providing local signals would include a detecting device or sensor directly or indirectly sensitive to the alert terminal signals or otherwise capable of signifying the receipt of the normal calling signals.

Preferably means, such as a monostable circuit, is also provided to provide electrical pulses corresponding to the number of normal calling signals, e.g., rings of the telephone bell. The assessing means can then include one or more counters for counting the locally generated pulses. A timer preferably provides time dependent signals which may be initiated by the original calling signals.

The use of such a timer and the pulse counters permits a code to be set up which may comprise two separate calling signals which may also occur-within a pre-determined time of one another. This type of code would preclude the possibility of other calls inadvertently actuating the control means. The control system preferably employs means, such as rotary selector switches, for re-adjusting the code from time to time. The time interval between successive calling signals can vary quite widely if desired and a timer may be unnecessary. However, it may be preferable then to have more than two pre-determined numbers of calling signals. For example, a code may comprise two pre-determined number of calling signals which occur within a time slot in minutes or a code may comprise say four pre-determined numbers of calling signals which occur over a much longer time interval.

In one embodiment of the invention the control means actuates switch means, which is preferably an electronic device such as a triac. The switch means can then be switched on and off by dialling the number of the telephone one or more times and allowing the telephone to ring a set number of times each time a connection is established.

It is desirable to electrically isolate the switching means, usually mains operated, from the control means. To this end the control means may include a light-emitting diode and a photo-electric device which changes resistance when the light-emitting diode is operated to actuate the switching means.

It is desirable for the control system to also employ means for checking the operative state of the appliance or switching means conveniently in response to a further calling signal or signals. This checking means may, in one form, include means for providing an audible tone when the switching device is conductive and means for raising the telephone handset of the associated telephone or for otherwise establishing a recordable or chargeable telephone line connection to permit the audible tone to be heard at a remote calling telephone.

In accordance with another aspect of the invention a method of controlling the operation of an electrical appliance in response to a remotely initiated action; comprises the steps of providing a sequence of normal calling signals but representing a pre-settable code to a telephone as said remotely initiated action, generating digital signals locally to the telephone but independently thereof in response to said sequence of normal calling signals, assessing with logic means whether said local signals are indicative of said code and operating control means to control said appliance independently of the telephone when said local signals are indicative of said code.

The invention may be understood more readily and various other features of the invention, may become apparent from consideration of the following description.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings wherein: Figure 1 is a schematic representation of a control system made in accordance with the invention; and Figure 2 is a graphical representation of the various time intervals and logic signals pertaining to the operation of the system shown in Figure 1.

As shown in Figure 1 of the accompanying drawings, a control system constructed in accordance with the invention is composed of the following components and devices: 1 Microphone MIC 1 Audio Amplifier AMP 1 Loudspeaker L.S 2 Light-emitting diodes LED and LED2 1 Monostable circuit device MONO 1 Microswitch MSW 1 Spring-biased switch SW2 1 Bistable circuit device FFI 2 J.K.Flip-flop circuit devices FF2 and FF3 2 Binary-to-decimal converter devices CON 1 and CON2 2 Counting circuit device COUNTI and COUNT2 1 Timing Device TM 4 Bistable latching circuit devices LAl-LA4 1 Inverter INV 3 AND gates AND l-AND3 4 NOR gates NORl-NOR4 2 OR gates ORI andOR2 1 N-P-N Transistor TR I Relay-REL (with switch contacts RELSWI and RELSW2) 1 Tone Generator TON I Triac TRI 1 Photo-electric cell PC 1 Motor MOT 1 Telephone handset raising and lowering mechanism 10 1 ON-OFF switch SWI 1 Outlet Socket SKT and 3 Rotary selector switches RS1, RS2 and RS3 The control system as illustrated is associated with a conventional telephone (not shown). The operation of the control system is governed by three predetermined parameters which are conveniently adjustable and pre-set by means of the selector switches RS1, RS2 and RS3. The first of these parameters, designated Rl and set by the switch RSI, is the first number of double rings of the bell of the telephone associated with the system. The second of the parameters, designated R2 and set by the switch RS2 is the second number of double rings of the telephone bell which follows the first number of rings Rl. The third of the parameters, designated T and set by the switch RS3, is the time period between the first double ring in the first number of rings Rl and the beginning of the time period during which the second number of rings R2 must be received.The choice of the three parameters Rl, R2 and T represents a code whereby, in this particular system some appliance can be controlled via the socket SKT.

The switches RSI, RS2 have twelve respective positions corresponding to the numbers Rl, R2 but, for reasons discussed hereinafter, the scale on these switches carries legends 2 to 13 so that by selecting say 6 as a number of rings Rl or R2 on the respective scale the actual number of rings selected is 5, i.e. Rl-l (R1-l) or R2 minus (R2-1). The switch RS3 also has twelve positions corresponding to the time in minutes.

Assuming that the system is to control, i.e., switch on or switch off the associated appliance connected to the socket SKT then the switch SWI is made and the switch SW2 is made to clear the device FF3. The telephone handset is left on its rest, the microphone MIC is placed near to the telephone so as to pick up the ringing of its bell and the loudspeaker LS is arranged near the telephone mouthpiece. The output from the microphone MIC is amplified by the amplifier AMP and is used to trigger the monostable device MONO which produces a series of countable pulses routed through the system. The device MONO is designed to change state, and provide complementary output pulses, one for each double ring of the telephone bell.The light-emitting diode LEDI is connected to one of the outputs from the device MONO and is used to check visually that the device MONO is producing the desired output pulses when the telephone bell rings. The other output from device MONO is connected to the input of the counting devices COUNTI and COUNT2 and to the start input of the timing device TIM. The counting device COUNT2 operates whenever the device MONO produces an output pulse while the counting device COUNTI operates only when enabled by a logic 'I' at its control input R. The device COUNTI is designed, when enabled, to produce an output only when three or more pulses are received at its input S while the device COUNT2 produces a continuous prevailing period.The device COUNT2 is designed to produce a binary coded output signifying the number of pulses, and hence double rings, in the prevailing period and this binary output is converted by the converter CONI to a decimal code on output leads 1--12 thereof.

These output leads 1--12 from the converter CONI are successively earthed (logic '0') to signify the number of pulses and hence double rings that have occurred. The leads 1--12 are respectively connected to the stationary contacts of both the switches RS I, RS2. As mentioned previously when the switches RS 1, RS2 are set to the desired positions Rl and R2 the stationary contacts actually selected are those corresponding to RI-I and R2-l. This is necessary because a remote caller dialing the correct telephone number may not necessarily hear the exact number of rings which have occurred.For example, when 3 double rings are heard either 2, 3 or 4 double rings may have actually occurred at the telephone associated with the control system. When the telephone bell first commences to ring the timing device TIM is started. At output C the timing device TIM provides clock pulses comprising a logic '1' present for 59.9 secs. of every minute followed by a logic '0' for the remaining 0.1 secs of the minute. This waveform is shown in Figure 1 and Figure 2 of the drawings. In addition, the device TIM provides a continuous main output in binary code representing the time elapsed in minutes from the first ring of the first number of rings Rl. This binary coded output is converted by the converter CON2 to a decimal code on output leads 1--12 thereof.These output leads 1--12 are successively earthed (logic '0') in accordance with the time elapsed and the leads are respectively connected to the stationary contacts of the switch RS2. An output R the device CON2 provides, in response to the timer TIM a logic '0' for the first minute of operation followed by a logic '1' (Figure 2).

With the system set up as described a remote caller checks the time, dials the telephone number and lets the telephone ring the desired number of times (Rl).

The caller waits for the prescribed time T from the time he started the first dialling sequence and re-calls the number letting the telephone ring and the desired number of times (R2). It can be assumed that this sequence of events will result in a conductive path to the live terminal L of the socket SKT becoming established to energize the appliance as desired. Figure 2 is useful in showing the various signals and time intervals which occur during operation of the system.The operation of the system when the events set forth above take place is as follows: When the first number of double rings reaches Rl-l the NOR gate NORI receives logic '0' at each of its inputs and its output logic '1' triggers the latching device LAl so that its output Q becomes logic '1'. This, in turn, provides a logic '1' at one input of the AND gate AND2 and triggers the latching device LA3 so that its output Q becomes. logic '1'. Thence, the OR gate OR2 provides a logic '1' to the control input of the counting device COUNT to enable the latter.If the number Rl is correct the counting device COUNT counts just the pulses respectively representing R1-l, and Rl and possibly Rl plus I (Rl+l). Only if the number of double rings exceeds Rl+l and is therefore incorrect will the latching device LAI be re-set by a logic '1' from the output of the device COUNTI and this will in due course prevent the AND gate 2 from providing an enabling output to the device FF3 when the second number or rings R2 occurs. The output logic 'I' from the device COUNTI will also re-set the monostable device MONO via the device FFI to prevent the device COUNT1 from counting out again.Assuming however that the count Rl+l is not exceeded the latching device LA1 remains with output Q as logic '1' whereas the latching device LA3 is reset when the output R from the device CON2 changes to logic '1' after the end of the first minute. The counter COUNTI will now be reset as the output from the OR gate OR2 becomes logic '0' in response to the logic '0' at the output of the device LA3. The AND gate AND I also resets the Counter COUNT2 when the output R of the device CON2 changes to logic '1' since the wiper of switch RS2 will at this time ( < T) be a logic 'I' also.

At the set time T from the start of the first number of rings the signal on the wiper of the switch RS3 changes to logic '0' (Figure 2). Then during the second number of double rings R2 the signal on the wiper of the switch RS2 becomes logic '0' when the new count reaches R2-1. The NOR gate NOR2 thus receives logic '0' at both inputs so its consequential output logic 'I' triggers the latching device LA2 so that its output Q becomes logic '1'. The AND gate AND2 now receives logic '1' at both inputs and the flip-flop device FF3 can change state when its trigger input is operated. The NOR gate NOR3 also now receives logic '0' at both its inputs and starts the counting device COUNT I since the output from the OR gate OR2 is logic '1'.As before, if R2+1 is exceeded the output from the counting device COUNTI will re-set both the latching devices LAI, LA2 to disable the AND gate AND2 and this output will reset the device MONO. Otherwise if we assume that R2 also checks out correctly the device FF2 will be triggered as follows. When the time T is initially reached, the inverter INV provides logic '1' at the inputs of the flip-flop device FF2. At this time the output Q is logic '0' and the output Q is logic ' I ' while the control pulse from output C of the timing device TIM is at logic '1' (Figure 2).

The device FF2 can only be triggered when the control pulse actually changes from logic '0' to logic '1' and this will occur at T+l minutes. This allows time for the counting device COUNTI to reset the devices L I, L2 if the subsequent count based on R2 is incorrect. The triggering of the device FF2 at T+ I changes its output Q to logic 'I' and its output Q to logic '0' (Figure 2). The output Q now in turn triggers the device FF3 since its associated AND gate AND2 signifies that both counts Rl and R2 and the time T therebetween have been assessed as being correct.The output Q from the device FF3 then changes to logic '1' thereby energizing LED2. The control means or circuit composed of LED2 and the photo electric cell PC (here in series with a resistor R) and the switching means or triac TRI form a convenient isolator between the mains supply and the logic devices etc., of the system. The light emitter by LED2 causes the photo-electric cell PC to change its resistance to an extent designed to trigger the triac TRI into conduction.

This provides a current path for the live supply L to the socket SKT and hence the appliance is switched on. At time T+i the AND gate ANDI receives logic '1' at both its inputs and hence resets the counter COUNT2. Also the NOR gate NOR3 provides a logic '0' to the OR gate OR2 so that the resultant logic '0' from the output thereof resets the counter COUNT. At time T+l when the control pulse from output C of the timer T changes from logic '0' to logic '1' to trigger or clock the devices FF2 and FF3 the NOR gate 2 is disabled since the signal on the wiper of the switch RS3 changes to logic '1'. At the same time the inverter INV provides logic '0' to the input of the device FF2.The devices LAI, LA2 are also reset when the output Q from the device FF2 changes to logic '1' but the devices FF2 and FF3 both remain with their output Q at logic 'I' until at time T+ 1-0.1 secs when the control pulse from output C of the timer T changes from logic ' I' to logic '0'. This clears or resets the device FF2 so that its output Q reverts to logic '0'. The device FF3 remains with its output Q at logic '0' however and LED2 remains energized. At the time T+ 1-0.1 secs when the output Q from the device FF2 reverts to logic '0' the corresponding change in the output Q of the device FF2 from logic '0' to logic '1' will stop and reset the timer TIM.A final reset pulse from the timer TIM is applied to the device FFI and thence to the device MONO to ensure the device MONO is ready for the next operative cycle.

If a caller re-calls with the correct code subsequently the same sequence of events will occur as described except that the trigger to the device FF3 will result in the output Q changing from logic to logic '0'. LED2 will thus switch off the triac TRI to thereby switch off the appliance.

The system as depicted also has facilities for permitting a remote caller to check that the desired control action has taken place and whether the appliance is switched on or off. This is accomplished by the caller re-calling the telephone number regardless of the code at any time during the T+ I to T+2 minute period except for the final reversion time of 0.1 secs or subsequently by making two successive calls separated by the time T but avoiding Rl and R2. In the latter case the requirement is merely to ensure that the inverter INV provides the logic '1' input to the device- FF2 at time T.The first ringing of the telephone bell with the output Q from the device FF2 at logic '1' will result in a pulse-logic '1' at the output of the device MONO which causes the AND gate AND3, also receiving logic 'I' as its other input, to produce a logic '1' output to operate the latching device-LA4. The output Q from the device LA4 becomes logic '1' while the output Q becomes logic '0'. Since the Q output from the device FF3 is also a logic '0' when the triac TRI is conductive the NOR gate NOR4 provides a logic 15 output to energize the tone generator TON. At the same time the logic 'I' at the output Q of the device LA4 triggers the transistor TR which hence actuates the relay REL which in turn closes the switch contact REL SWI and REL SW2. The motor MOT is thus also energised simultaneously with the tone generator TON.The motor MOT is connected to an eccentric mechanism 10 designed to lift and replace the handset from its rest, several, say eight times per minute so that the remote caller can periodically hear the tone provided by TON signifying that the appliance is switched on. The microswitch MSW is closed or made when the handset is lifted and opened when the handset is at rest. In the case where the appliance is off the output Q of the device FF3 is logic '1' hence disabling the NOR gate NOR4. The sequence of events will then repeat except that the tone generator TON will be inoperative so the caller will merely hear the handset being repeatedly lifted.When the clock pulse from the output C of the timer TIM changes to logic '0' during the last 0.1 secs of the T+ I minute the device LA4 is reset by the logic '1' at output Q of the device FF2, thereby causing the tone generator TON (if operating) and the relay REL to become inoperative, while the AND gate AND3 produces a logic '0' output in response to the change in the output Q of the device FF2 from logic '1' to logic '0'. The motor MOT is maintained in an operative state when the contacts REL SW2 open by the microswitch MSW. Thus the motor MOT continues to operate until the handset is actually replaced to open the microswitch MSW and halt the motor MOT.

The actions performed by the remote caller can be summarized as follows: Assuming that the appliance connected to the socket SKT is to be switched on or off the caller firstly dials the number of the telephone noting the time when he starts to dial. He then allows the telephone to ring Rl times and then he calls off.

When time T has elapsed he re-dials the number of the telephone and he allows the telephone to ring R2 times before finally calling off. As described before the appliance will be switched on or off as desired. To check the state of the appliance, i.e., whether it is switched on or off, the caller can at any time dial the telephone number letting the telephone ring preferably less than Rl times and again noting the time. When T+ I minutes have elapsed, when FF2 is triggered and its output Q is logic '1', the caller re-dials the telephone and allows it to ring preferably less than R2 times. The telephone handset will then be raised periodically and if he hears the tone provided by the tone generator TON the appliance is on: otherwise the appliance is off.The caller can also check whether the system has operated by redialling the telephone number a third time, following the two calls where he let the telephone ring RL and R2 times respectively, so long as this third call is made within the time T+l to T+2.

The various devices of the control system can be fabricated as one or more integrated circuits although conventional components or other, e.g., thin or thick film, techniques can be adopted. Certain modifications can be made to the system.

For example, the control system can be incorporated or combined with a telephone answering machine. The timing device TIM can also be designed to provide additional time dependent control functions for example to reverse the switching action performed by the system on the appliance after a set time has elapsed or to inhibit the overall system except for a certain time period during the day. The system can also be adapted to actuate various other forms of devices and/or control means; for example the system can be used with a time clock or a speed controller.

WHAT I CLAIM IS: 1. A control system for controlling the operation of an electrical appliance in response to a remotely initiated action; said system comprising means for providing local digital signals in response to a sequence of normal calling signals provided to a telephone associated with the system but independent of the appliance as a result of said remotely initiated action, logic means for assessing said local signals to detect whether said local signals indicate a correct pre-settable code imparted by the sequence of calling signals and control means selectively operated by the assessing means to control said appliance.

2. A control system according to claim 1, wherein the control means is arranged to actuate switching means connected to switch said appliance on or off.

3. A control system according to claim I or 2, wherein the means for providing local signals includes a detecting device directly or indirectly sensitive to the reception of the normal calling signals by the telephone and means providing pulses corresponding to the number of calling signals.

4. A control system according to claim 3, wherein said detecting device is directly or indirectly sensitive to the alert terminal signals provided by the telephone in response to said calling signals.

5. A control system according to claim 3 or 4, wherein the detecting device is a microphone.

6. A control system according to claim 3, 4 or 5, wherein the assessing means is adapted to at least count the pulses corresponding to the number of calling signals.

7. A control system according to any one of claims I to 6, wherein the means providing the local signals includes a timer device which produces time dependent signals initiated by said sequence of calling signals.

8. A control system according to any one of claims I to 7, wherein the correct code assessed by the assessing means comprises two or more pre-determined numbers of pulses corresponding to two or more sequences of calling signals which occur within a pre-determined time period of each other.

9. A control system according to any one of claims I to 7, wherein the correct code assessed by the assessing means comprises two or more pre-determined numbers of pulses corresponding to two or more separate sequences of calling signals.

10. A control system according to claim 8 or 9, wherein the assessing means is adapted to inhibit the control means if either or both the two or more predetermined number of pulses is exceeded by a pre-set number.

11. A control system according to claim 7, wherein the timer device provides clock pulses which serve to enable the control means after the correct code has been detected.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (21)

**WARNING** start of CLMS field may overlap end of DESC **. starts to dial. He then allows the telephone to ring Rl times and then he calls off. When time T has elapsed he re-dials the number of the telephone and he allows the telephone to ring R2 times before finally calling off. As described before the appliance will be switched on or off as desired. To check the state of the appliance, i.e., whether it is switched on or off, the caller can at any time dial the telephone number letting the telephone ring preferably less than Rl times and again noting the time. When T+ I minutes have elapsed, when FF2 is triggered and its output Q is logic '1', the caller re-dials the telephone and allows it to ring preferably less than R2 times. The telephone handset will then be raised periodically and if he hears the tone provided by the tone generator TON the appliance is on: otherwise the appliance is off.The caller can also check whether the system has operated by redialling the telephone number a third time, following the two calls where he let the telephone ring RL and R2 times respectively, so long as this third call is made within the time T+l to T+2. The various devices of the control system can be fabricated as one or more integrated circuits although conventional components or other, e.g., thin or thick film, techniques can be adopted. Certain modifications can be made to the system. For example, the control system can be incorporated or combined with a telephone answering machine. The timing device TIM can also be designed to provide additional time dependent control functions for example to reverse the switching action performed by the system on the appliance after a set time has elapsed or to inhibit the overall system except for a certain time period during the day. The system can also be adapted to actuate various other forms of devices and/or control means; for example the system can be used with a time clock or a speed controller. WHAT I CLAIM IS:

1. A control system for controlling the operation of an electrical appliance in response to a remotely initiated action; said system comprising means for providing local digital signals in response to a sequence of normal calling signals provided to a telephone associated with the system but independent of the appliance as a result of said remotely initiated action, logic means for assessing said local signals to detect whether said local signals indicate a correct pre-settable code imparted by the sequence of calling signals and control means selectively operated by the assessing means to control said appliance.

2. A control system according to claim 1, wherein the control means is arranged to actuate switching means connected to switch said appliance on or off.

3. A control system according to claim I or 2, wherein the means for providing local signals includes a detecting device directly or indirectly sensitive to the reception of the normal calling signals by the telephone and means providing pulses corresponding to the number of calling signals.

4. A control system according to claim 3, wherein said detecting device is directly or indirectly sensitive to the alert terminal signals provided by the telephone in response to said calling signals.

5. A control system according to claim 3 or 4, wherein the detecting device is a microphone.

6. A control system according to claim 3, 4 or 5, wherein the assessing means is adapted to at least count the pulses corresponding to the number of calling signals.

7. A control system according to any one of claims I to 6, wherein the means providing the local signals includes a timer device which produces time dependent signals initiated by said sequence of calling signals.

8. A control system according to any one of claims I to 7, wherein the correct code assessed by the assessing means comprises two or more pre-determined numbers of pulses corresponding to two or more sequences of calling signals which occur within a pre-determined time period of each other.

9. A control system according to any one of claims I to 7, wherein the correct code assessed by the assessing means comprises two or more pre-determined numbers of pulses corresponding to two or more separate sequences of calling signals.

10. A control system according to claim 8 or 9, wherein the assessing means is adapted to inhibit the control means if either or both the two or more predetermined number of pulses is exceeded by a pre-set number.

11. A control system according to claim 7, wherein the timer device provides clock pulses which serve to enable the control means after the correct code has been detected.

12. A control system according to any one of claims 1 to 11, wherein the

control means includes a light-emitting diode and a photo-electric device.

13. A control system according to claim 12, when appended to claim 2, wherein the switching means comprises a triac triggered by the photo-electric cell when the light-emitting diode operates.

14. A control system according to any one of claims 1 to 13, wherein there is further provided means for checking the state of the appliance in response to a further calling signal or signals.

15. A control system according to claim 14, wherein the checking means includes means for providing an audible tone whenthe appliance is operating and means for raising the telephone handset of the associated telephone to permit the audible tone to be heard at a remote calling telephone.

16. A control system according to claim 14, wherein the checking means includes means for providing an audible tone when the appliance is operating and means for establishing a telephone line connection to permit the audible tone to be heard at a remote calling station.

17. A control system according to any one of claims 1 to 16 and further comprising means permitting re-adjustment of the code.

18. A control system substantially as described with reference to, and as illustrated in, Figure 1 of the accompanying drawings.

19. A method of controlling the operation of an electrical appliance in response to a remotely initiated action; said method comprising the steps of providing a sequence of normal calling signals but representing a pre-settable code to a telephone as said remotely initiated action, generating digital signals locally to the telephone but independently thereof in response to said sequence of normal calling signals, assessing with logic means whether said local signals are indicative of said code and operating control means to control said appliance independently of the telephone when said local signals are indicative of said code.

20. A method according to claim 19, wherein the code comprises two or more pre-determined numbers of pulses corresponding to calling signals.

21. A method of controlling the operation of an electrical appliance substantially as described herein.