CA1078494A - Dual temperature control circuit - Google Patents

Abstract

DUAL TEMPERATURE CONTROL SYSTEM

ABSTRACT OF THE DISCLOSURE
A temperature control system for providing an automatic reduction in the temperature of a room or a house during the nighttime hours which requires only the con-ventional two conductor wiring between the furnace and the thermostat thereby avoiding the necessity of adding to or replacing the existing wiring between the furnace and the thermostat. A first embodiment of the system includes a temperature responsive element, a heater near the tem-perature responsive element for providing supplemental heating of the element, a conventional furnace control, a clock-operated current control for the heater, and a diode steering circuit for directing one portion of an alternating current waveform through the heater current control and the heater, and another portion of the alternating current waveform through the temperature responsive element and the furnace control for providing independent control of the heater and the furnace control. The heater provides supplementary heating of the temperature responsive element during the night-time hours to establish an apparent room temperature which is higher than the actual room temperature so that the thermo-stat element will lower the room temperature during the nighttime hours. A second embodiment of the system includes two temperature responsive elements, one for setting the low temperature and the other for setting the high temperature, a conventional furnace control, a clock-operated switch for activating either the high or low temperature responsive element, and a diode steering circuit for directing one portion of an alternating current waveform through the low temperature responsive element and the furnace control, and another portion of the alternating current waveform through the high temperature responsive element and the furnace control for providing independent control of the furnace by the low temperature element and the high temperature element in accordance with the timer switch. Accordingly, the low temperature responsive element may be set at the desired nighttime temperature and the high temperature responsive element can be set at the desired daytime temperature with each being activated for the appropriate time period by the timer switch.

Description

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BACKGROUND }~ND SUMMARY OF THE INVENTION ~r~ ~
The present invention relates to a system for ~:
automatically lowering the temperature of a room or a house during certain periods such as the nighttime hours utilizing the conventional two-conductor wiring ~rom the furnace to the thermostat control. In this regard, it will be appreciated that in view of the national need to conserve energy, it is highly recommended that home temperatures be lowered every evening. As a practical matter, homc owners will be less . : .

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likely to effect a nightly tempcrature reduction if he must rcmelnbcr to adjust the thcrmostat each night and must arise to a cold house cach morning and then readjust the thermostat.
Consequently, the advantages of an automatic system for reducing the t~mperature setting of the thermostat each night and fo~r increasing the temperature setting just prior to the usual awakening time are apparent:.
It will be appreciated that if the installation of an automatic system requires the trouble and expense of replacing or supplementing the existing wiring from the thermostat to the furnace, or the automatic system is costly~
home owners will be discouraged rather than encouraged to save energy through the installation of an automatic tem-perature reduction system.
The present invention provides an automatic tem-perature reduction system for a room or house which is straight-forward in construction so that it may be manufactured at low cost, and additionally, utilizes the two existing conductors of the conventional thermostat wiring. A first embodiment of the present invention achieves these advantag ~ us results by providing a temperature control system utilizing a heat source which is associated with the temperature re-sponsive element in the heated area and which is activated during the nighttime hours to make the apparént room tem-perature appear to be higher than the actual room temperature thereby causing the temperature responsive element to signal for a reduction in room temperature. A clock-controlled adjustable current source for the heater is locat~d near the usual furnace control. Steering circuitry such as a :~07~

first pair oE diodes at ~ho ~urnace control and heater current source location and a sccond pair of diodes at the temperature responsive element and hcater location is provided for directing one-half of an alternating current waveform through the furnace control and the temperature responsive element, and the other half of the alternating current waveform through the heater current source and the heater so that the furnace temperature control can be independently controlled by the temperature responsive element and the heater can be in~
dependently controlled by the heater current source by using respective halves of the waveform for each control functio,n.
A second embodiment of the present invention achieves the same advantages and results obtained by the first embodi- -ment of the present invention by providing a temperature control system utilizing a pair of temperature responsive elements in the heated area, one beiny set at the desired daytime temperature and the other being set at the desired nighttime temperature. The temperature responsive elements are activated during the appropriate period by a timer switch which includes a pair of switched contacts. A first of t~e s~itch contacts is associated with the nighttime temperature responsive element by means of a diode steering circuit and the second set of contacts is associated with the daytime temperature responsive element by the diode steering circuit.
The steering circuit may include a first pair of diodes associated with the timer switch and a second pair of diodes associated with the temperature responsive elements. One of each pair of diodes is arranged in polarity so that a ' current path for one-half of the alternating current waveform ~.~'7~9~9~

is providcd throu~h ono set of the timer switch contacts thc hi~3h tc~ L~erature responsive clemcnt and the furnace control. The other diode of each pair is arranged in polarity so that a current path for the other half of the alternating current waveform is provided through the other set of the timer switch contacts, the low temperature responsive element and the furnace control. Accordingly, each of the temperature responsive elements is independently associated wlth the furnace control at times determined by the closing of the contacts of the timer switch. The second embodiment of the present invention is also provided with an override switch which bypasses the diode associated with the high temperature responsive element so that the high temperature responsive -element controls the furnace control at all times. In this regard, when the override switch is closed, the circuit through the furnace control will not be interrupted until the high temperature responsive element opens the circuit, e.g., when the high temperature is exceeded, regardless of which timer switch contact is closed.

BRIEF DESCRIPTION OF THE l:~RAWING
Figure 1 is a schematic illustration of a first embodiment of a temperature control system according to the present invention; and - Figure 2 is a schematic illustration of a second embodiment of a temperature control system according to the present invention.

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In Figure 1, a tcmpcraturc control system 10 is illustrated which includes a first unit or system portion 12 which is located in the room or area in which the temperature is to be controlled, and a second unit or system portion 14 which is located proximate the furnace. The units 12 and 14 are connected by a single pair of conductors 16 and 18 which may be the pre-existing wiring from a conventional home thermostat unit. The unit 14 receives standard alternating current energy of 110-120 volts on conductors 20 and 22.
The unit 14 includes a step-down transformer 24 which converts the 110-120 volt alternating current energy to approximately 24 volts of alternating current energy across conductors 26 and 28. The unit 14 further includes a tem-perature control relay or solenoid switch 30 having a relay coil 32 and relay contacts 34 which are connected in series with a furnace control conductor 36 which in turn is connected to a conventional furnace control so that the furnace is turned on to supply heat to the heated area upon powering of -~he relay 30 which closes relay contacts 34. A spike suppression `
capacitor 37 is connected across the relay coil 32. The unit 14 still further includes a heater control unit 38 which consists of a timer motor 40, which controls timer contacts 42, and a variable resistor 44.
The unit 12 includes a thermostat switch 46 such as a conventional bi-metal element which is adapted to bend in one direction on cooling to a preset temperature to close the switch and to bend in the other direction on heating to a somewhat hiyher temperature. The unit 12 further includes . :

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a heating unit 48 which may be an incandcscent lamp bulb or the like. Thc hea~er 98 is in thcrmal transfer rclation-ship with the thermostatic switch 46 so that the thermostatic switch 46 is heated by the heater 48 to make the room tem-perature or house temperature appear higher when the heater 48 is operated.
Each of the relay coil 32, the variable resistor-44, and the timer controlled contacts 42, the heater control unit 38, the heater 48, and the thermostatic switch 46 are connected to the two conductors 16 and 18 and the alternating current source on conductors 26 and 28 by a steering circuit which includes diodes 50, 52, 54 and 56. More particularly, the diode 50 is connected in parallel with the relay 32 and the spike suppression capacitor 37 and is connected in series with the supply line 26 and the conductor 16. The diode 52 is connected in parallel with a series connection .of the variable resistor 44 and the timer controlled switch 42, and in series with the supply conductor 28 and the con-ductor 18. The diode 54 is connected in series with the heater 48, and across the existing conductors 16 and 18 so that it is in parallel with the temperature responsive switch 46. The diode 56 is connected in series with the temperature responsive switch 46, and across the conductors 16 and 18 so that it is in parallel with the heater 48.
In view of the above connection of the diodes, it will be appreciated that the positive-going portion of the potential waveform on supply line 26 provides a current which flows through diode 50, diode 54, heater 48, timer controllcd contacts 42, and the variable resistor 44 to ,, ~r7849~

thè other supply line 28. Negligible current flows through the temperature controlled relay coil 32 since the voltage drop across the forward-biased diode SO is very small, and no current flows through the termostatic switch 46 since the diode 56 is reversed biased.
O When a positive-going portion of the potential waveform appears on the supply line 28, a current flows through the diode 52, the ~hermostatic switch 46, the diode 56, and the temperature controlled relay coil 32 to the other supply line 26. Negligible current flows through the adjustable resistor 44 and the timer controlled switch 42 since the voltage drop across the forward-biased diode 52 is very small, and no current flows through the heater 48 since the diode 54 is back biased.
- In view of the above, it will be appreciated that the time-varying, alternating current voltage waveform pro-vided by the step-down transformer 24 on lines 26 and 28 is divided into two time displaced portions, with one portion being directed through the circuit including the thermostatic switch 46 and the temperature controlled relay 32 and the other portion being directed through the heater 48~ the timer controlled switch 42, and the heater control variable resistor 44. As a result, the furnace and the heater 48 can be independently controlled.
In operation, the user sèts the thermostat switch 46 for the appropriate daytime room temperature. As explained above, the thermostatic switch 46 operates in conjunction with ~he temperature control unit 30 to control the operation of the furnace through the opening and closing o~ the furnace ` !
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control switch 34. The user als~ set~ the timer motoX so that the switch 42 is closed during the nighttime hours and sets the variable resistor 44 to establish the number o~
degrees of reduction of the nighttime temper~ture in the heated area. Preferably, the variable resistor is calibrated in degrees. For example, the calibr~tion can be between 0 and 20 degrees reduction in nighttime temperature with increasing resistance establishing a decreasing number o~
degrees of reduction of the nighttime temperature and infinite resistance, i.e. an open at the resistor 44, providing no reduction in nighttime temper~ture. If desired, a switch 45 may ~e placed in series with the ~ariable resistor 44 which is openable to provide a means for overriding the automatic nighttime temperature reduction. Alternatively, or in addition to the switch 45, a switch 55 may be placed in series with the diode 54 and the heater 48 which is openable to override the automatic nighttime reduction. By opening either the switch 45 or the switch 55, the heater circui~ is open-circuited so that the heater will not receive energizing current.
During the periods in which the timer controlled switch 42 is closed, current will flow through the heater 48 in an amount determined by the setting of the variable resistor 44 to cause supplemental heating of the temperature responsive switch 46. The supplemental heating of the temperature responsive switch 46 makes the apparent temperature o~ the heated area to appear high~r than the actual temperature.
Accordingly,! the temperature responsive switch 46 will xeact to cause a decrease in the actual temper~ture o~ the heated area in accordance with the amount o~ heating of the temperature responsive switch 46 by the heater 48, and accordingly, in accordance with the amount of current flowing _g_ :

784~4 through the heater 48 as established by the settin~ o~ the variable resistor 44. The closing and opening o~ the tem-perature responsive switch 46 is responsible for the closin~
and opening of the relay switch 34 so ~s to turn the ~urnace on whenever the temperature falls below the set temperature and turn the furnace off when the temperature rises above a temperature slightly above the set temperatureO
In Figure 2, a second embodiment of a temperature control system 60 is illustrated which includes a first unit or system portion 62 which is located in the room or area in which the temperature is to be controlled, and a second unit or system portion 64 which is located proximate the furnace.
The units 62 and 64 are connected by a single pair of con-ductors 16 and 18 which may be the pre-existing wiring from a conventional home thermosta~ unit. The unit 64 receives standard alternat~ng current energy of 110-120 volts on conductors 70 and 72. ,' The unit 64 includes a step-down transformer 74 which converts the 110-120 volt alternating current energy to approximately 24 volts of alternating current energy ,across conductors 76 and 78. The unit 64 further includes a temperature-control relay or solenoid switch 80 having a relay coil 82 and relay contacts 84 which are connected in :
series with a furnace control conductor 86 which in turn is connected to a conventional furnace control so that the furnace is turned on to supply heat to the heated area upon powering of the relay 80 which closes relay contacts 84. A
spike suppression and iltering capacitor 87 i~ connected across the relay coil 82. The unit 64 stlll furthex includes a dual thermostat control unit having a timer solenoid 90 which controls a nighttime timer contact 92 and a da~time , --10 .
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~78499t timer contact 94. The contacts 92 and 94 are synchxonousl~
opened and closed fo~ mutually respective pexiods by a single mechanical connection as schematically illust~ted, i.e., contact 92 opens when contact 94 closes and Vise Versa.
The unit 62 includes a pair of thermostat switches 96 and 98 with each switch 96 and 98 having, for example, a conventional bi-metal element which is adapted to bend in one direction on cooling to a preset temperature to close the switch and to bend in the other direction on heating to a somewhat higher temperature to open the switch. The thermo-stats 96 and 98 are preferably mounted in the same enclosure and are marked for day and nighttime temperatures. Each of the thermostats 96 and 98 may be independentl~ set to the desired temperature for daytime and nighttime, respectively.
Each of the rela~ coil 82, the timer controlled contacts 92 and 94, and the thermostatic switches 96 and 98 are connected to the two conductors 16 and 18 and he alternating current source on conductors 76 and 78 by a steering circuit which includes diodes 100, 102, 104 and 106. More particularly, the diode 100 is connected in series with d~ytime contacts 94 of the dual thermostat control unit 88 and is connected in parallel with the nighttime contacts 92 of the dual thermostat control unit 88. The diode 102 is connected in series with the nighttime contacts 92 of the dual thermostat control unit 88 and is connected in parallel with the day-time c~ntacts 94 o the dual thermostat control unit 88.
~he diode 104 is connected in series with the low temperature thermostat 98 in parallel with the hi~h temperature thermostat 96. The diode 106 i.s connected in series with the high temperature thermostat 96 and ln parallel with the low tem-perature thermostat 98.

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In view of the above conncction of diodes, it will be appreciated that the positive-going portion of the potential waveform Oll supply line 76 provides a current which flows through the furnace control 82, the d.iode 106, the daytime or high temperature thermostat 96, the diode 100, and the daytime~ timer controlled contacts 94 ~presuming the contacts 94 are closed in the timer solenoid 90) to the other supply line 78. During the positive half-wave on line 76, no current flows through the nighttime or low temperature thermostatic switch 98 since the diode 104 is reverse biased.
When a positive-going portion of the potential waveform appears on the supply line ~78, a current flows through the nighttime timer controlled contacts 92 (presuming the contacts 92 are closed by the timer solenoid 90), the nighttime or low temperature thermostatic switch 98, the diode 104 and the furnace control coil 82 to the other supply line 76. During the positive half-wave on line 78, no current flows through the daytime or high temperature thermostatic switch 96 since the diode 106 is reverse biased.
In view of the above, it will be apprecia~ed that j .
the time-varying, alternating current voltage waveform pro-vided by the step-down transformer 74 on lines 76 and 78 is divided into two time-displaced portions, with one portion being directed through the circuit including the low tem-perature thermostatic switch 98, the nighttime contacts 92 of the timer switch 88, and the temperature-control furnace relay 82, and the other portion being directed through the high temperature thermostatic switch 98, the daytime contacts 9~ of thc timer switch 88 and the furnace relay 82. As a ~L~71~49~

rcsult, thc furnace can be indepcndcn-tly controlled at respective timcs, as sct by thc clock-controlled switch 88, by the high and low temperature thermostats 96 and 98, respectively.
In operation, the user sets the thermostatic switches 96 and 98 for the appropriate daytime and nighttime room temperatures, respectively. As explained above, the thermostatic switch 96 operates in conjunction with the temperature control unit 80 to control the operation of the furnace through the opening and closing of the furnace control switch 84. The user also sets the timer solenoid 90 so that the contacts 92 are closed during the nighttime hours and the contacts 94 are opened during the daytime hours, and conversely, so that the contacts 92 are open during the daytime hours and the contacts 94 are closed during the daytime hours.
The control unit 62 is further provided with an override switch 108 which is connected in parallel with the diode 106 so as to provide bi-directional current flow through the daytime or high temperature thermostat 96 when it is closed. Closing of the override switch 108 eliminates the control function whereby the temperature is reduced during the nighttime hours. This is due to the fact that the furnace control switch 84 will be closed at any time there is current flowing through the solenoid coil 82, and in turn, current will flow through the solenoid coil at any time the temperature in the heated area is below the temperature-set at the high temperature thermostat 96. In this regard, consider the nighttime hours at which tim~ the daytime timer . j . .

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78~4 controllcd contacts 9~ are open and the ni~httimc timex control contacts 92 are closed which would normally result in operation of the furnace control 80 under the control of the low temperature thermostat 98. ynder those conditions, diode 106 would normally prevent any current from passing throug~ the high temperature thermostat 96 since it will be reverse biased. When the override switch 108 is closed, this current is no lon~er blocked by the diode 106 so that it will also pass through the high temperature thermostat 96 (presuming the contacts thereof are closed). So long as the temperature is below the temperature set by the high tem- i perature thermostat 96, the opening and closing of the low temperature thermostat 98 will have no effect on the opexation of the furnace since current will be continuously supplied to the furnace control solenoid coil 82 through the high temperature thermostat 96. Whenever the temperature in the heated area rises above the set temperature of the high temperature thermostat 96, the switch of the high temperature thermostat 96 will open to in~errupt the current through the furnace control solenoid coil 82 to turn off the furnace.
At this time, it is presumed that the temperature set on the low temperature thermostat 98 has alread~ been exceeded so that the switch of the low temperature thermostat 98 will already be open. Accordingly, the high temperature thermo-stat 96 will control the temperature in the heated area regardless of the opening and closing of the timer controlled contacts 92 and 94.
In view of the above description of the temperature control systcm according to the present invention, it will bc appreciated that thc system of this invcntion uses few ~~4 ~378~9~

components and that thc componcnts used are available at low cost. Consequently, the system c~n be constructed at low cost. Importantly, the system is adapted to utilize the existing two conductors in the wiring system of con-ventional thermostats so th~t the temperature control system according to the present invention may be easily installed at low cost.
It is to be understood that the foregoing des- -cription is that of the preferred embodiment of the invention.
Various changes and modifications may be made without de-parting from the spirit and scope of the invention as defined by the appended claims.

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Claims (19)

1. THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
   OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
   
   . 1. A system for controlling temperature at a first location from a remotely located second location utilizing a source of time varying electrical energy which alternates between two directions of current flow and two conductors ex-tending from said first location to said second location comprising:
   a first system portion located at said first location including temperature responsive means for responding to the temperature at said first location and a heat source in heat transfer relationship with said temperature responsive means for heating said temperature responsive means;
   a second system portion located at said second location including control means for said heat source and a temperature control means for controlling the temperature at said first location;
   and steering circuitry means for receiving said time varying electrical energy and for connecting said heat source control means to said heat source and said temperature responsive means to said temperature control means only through said two conductors, said steering circuitry means providing a first time period of said time varying electrical energy exclusively to said heat source control means and said heat source and a second time period of said time varying electrical energy exclusively to said temperature control means and said temperature responsive means for providing independent control of said heat source by said heat source control means and said temperature control means by said temperature responsive means.
2. 2. A system according to claim 1 wherein said time varying electrical energy is characterized by current which alternates between two directions of current flow and wherein said steering circuitry means includes means for directing current in one direction through said heat source control means and said heat source and for directing current in the other direction through said temperature control means and said temperature responsive means.
3. 3. A system according to claim 2 wherein said means for directing said current includes diode means.
4. 4. A system according to claim 3 wherein said diode means is a plurality of diodes.
5. 5. A system for controlling temperature at a first location from a remotely located second location utilizing a source of time varying electrical energy which alternates between two directions of current flow and two conductors extending from said first location to said second location comprising:
   a first system portion located at said first location including temperature responsive means for responding to the temperature at said first location and a heat source in heat transfer rela-tionship with said temperature responsive means for heating said temperature responsive means;
   a second system portion including control means for said heat source and a temperature control means for controlling the temperature at said first location; and steering circuitry means for receiving said time varying electrical energy and for connecting said heat source control means to said heat source and said temperature responsive means to said temperature control means through said two conductors, said steering circuitry means including current directing means for directing current in one direction through said heat source control means and said heat source and for directing current in the other direction through said temperature control means and said temperature responsive means for providing independent control of said heat source by said heat source control means and said temperature control means by said temperature responsive means, said current directing means causing current in said one direction to bypass said temperature control means and said temperature responsive means and current in said other direction to bypass said heat source control means and said heat source.
6. 6. A system according to claim 5 wherein said current directing means includes a first diode connected in parallel with said temperature control means to bypass said current in said one direction, a second diode connected in parallel with said temperature responsive means to bypass said current in said one direction, a third diode connected in parallel with said heat source control means to bypass said current in said other direction, and a fourth diode connected in parallel with said heat source to bypass said current in said other direction.
7. 7. A system according to claim 6 wherein said first and second diodes are connected in series with said heat source control means and said heat source to direct current in said one direction through said heat source control means and said heat source, and said third and fourth diodes are connected in series with said temperature control means and said temper-ature responsive means to direct current in said other direction through said temperature control means and said temperature responsive means.
8. 8. A system according to claim 1 wherein said heat source control means includes means for activating said heat source control means for a predetermined period.
9. 9. A system according to claim 8 wherein said means for activating said heat source control means includes a timing means with a switch operated by said timing means for connecting said heat source control means to said heat source during said predetermined period.
10. 10. A system according to claim 1 wherein said heat source control means includes a variable resistor for adjusting the magnitude of current through said heat source thereby adjusting the heat output of said heat source.
11. 11. A system according to claim 1 wherein said heat source is an incandescent lamp.
12. 12. A system for controlling temperature at a first location from a remotely located second location utilizing a source of time varying electrical energy which alternates between two directions of current flow and two conductors extending from said first location to said second location comprising:
    a first system portion located at said first location including temperature responsive means for responding to the temperature at said first location for providing control of temperature at said first location at a first temperature level and additional means for providing control of temperature at said first location at a second temperature level;
    
    a second system portion at said second location for controlling the temperature at said first location; and steering circuitry means for receiving said time varying electrical energy and for connecting said temperature responsive means and said additional means to said second system portion through said two conductors, said steering circuitry means including directing means for directing current in one direction through said temperature responsive means and said second system portion and for directing current in the other direction through said additional means and said second system portion for providing independent control of said temperature at said first location by said temperature responsive means and said additional means through said second system portion, said directing means causing current in said one direction to bypass said additional means and current in said other direction to bypass said temperature responsive means.
13. 13. A system according to claim 12 wherein said second system portion includes a first control means cooperative with said temperature responsive means for controlling the temperature at said first location at said first level and second control means cooperative with said additional means for controlling the temperature at said first location at said second temperature level, said steering circuitry means connec-ting said first control means to said temperature responsive means and said second control means to said additional means so as to direct current in one direction through said temperature responsive means and said first control means and to direct current in the other direction through said additional means and said second control means for providing independent control of said temperature responsive means by said first control means and said additional means through said second control means, said directing means causing current in said one direction to bypass said second control means and current in said other direction to bypass said temperature responsive means.
14. 14. A system according to claim 12 wherein said directing means includes diode means.
15. 15. A system according to claim 14 wherein said diode means is a plurality of diodes.
16. 16. A system according to claim 13 wherein said directing means includes a first diode connected in parallel with said first control means to bypass said current in said other direction, a second diode connected in parallel with said tem-perature responsive means to bypass said current in said other direction, a third diode connected in parallel with said second control means to bypass said current in said one direction, and a fourth diode connected in parallel with said additional means to bypass said current in said one direction.
17. 17. A system according to claim 16 wherein said first and second diodes are connected in series with said second control means and said additional means to direct current in said other direction through said second control means and said additional means, and said third and fourth diodes are connected in series with said first control means and said temperature responsive means to direct current in said one direction through said first control means and said temperature responsive means.
18. 18. A system according to claim 13 wherein said second control means includes means for activating said second control means for a predetermined period.
19. 19. A system according to claim 18 wherein said means for activating said second control means includes a timing means with a switch operated by said timing means for connecting said second control means to said additional means during said predetermined period.