US 3192507 A
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Description (OCR text may contain errors)
June 29, 1965 R. A. SUDGES 3,192,507
REMOTE CONTROL SYSTEM Filed Sept. 11. 1961 T- VOL TS STAGE 30 IN VE N TOR Richard A. Sudges OUTPUT VOL TS United States Patent 3,192,507 REMOTE CONTROL SYSTEM Richard A. Sudges, Chicago, Ill., assignor to Admiral Corporation, Chicago, 11]., a corporation of Delaware Filed Sept. 11, 1961, Ser. No. 137,135 6 Claims. (Cl. 340-171) This invention concerns remote control systems in general and in particular concerns a remote control system of a very simplified type having a single control channel.
The system of the invention provides an effective, economical and compact control unit which may be readily adapted for use with a great number of devices of which television receivers and air conditioners are illustrative examples.
While the invention will be described in connection with a control system responsive to ultrasonic control signals, it will be readily appreciated that other types of propagated signals may be employed, the only criterion being that the transmitter and the receiver portion of the con trol unit be compatible.
At present the use of ultrasonics for remotely control.- ling television receivers and the like has dominated the field. There are many reasons for the widespread acceptance of ultrasonics in such control systems, among them being the limited transmission range (no interference with neighboring sets) and the availability of hammer and rod type transmitters, which do not require a source of electric power.
However, such systems have inherent disadvantages, especially with respect to extraneous noise signals generated by jingling keys, telephone bells and the like. Hence, it is necessary to build into such units a relatively high degree of noise immunity. At the same time, the art has been rapidly moving towards more compact and economical control units, especially the type employing transistors which may be left continuously energized for immediate operation.
One such transistorized control unit having a high degree of noise immunity is disclosed in a co-pending application of Reuben C. Carlson et al., Serial No. 36,223, filed June 15, 1960, now US. Patent No. 3,027,497, issued March 27, 1962. In the above mentioned co-pending application the unit is designed to have at least two separate control channels. While such a unit could be readily adapted for a single control function, it would not prove economical to do so.
An object of this invention is to provide a very simple compact single channel control unit having a very high degree of noise immunity.
A further object of this invention is to provide a single channel control unit which is much more economical than any comparable device in the prior art.
Another object of this invention is to provide a novel means of improving noise immunity in a remote control system.
A still further object of this invention is to provide a control unit incorporating signal frequency discrimination, signal duration discrimination and signal amplitude discrimination.
These and other objects and advantages of this invention will be readily apparent upon reading the specification in conjunction with the drawing in which FIG. 1 is a schematic diagram of an ultrasonic control unit constructed in accordance with the teachings of the invention and FIG. 2 is a curve of signal output level versus signal input level for the amplitude discriminating stage of the above circuit.
Referring now to FIG. 1 of the drawing there is shown a block 5 which includes structure (not shown) for transmitting an ultrasonic control signal of particular frequency. It will be understood that this signal will have a predetermined minimum amplitude for a predetermined minimum duration.
The signal transmitted from transmitter 5 is received by a microphone 6 and converted to an electrical signal of corresponding frequency. Microphone 6 is preferably of the piezoelectric type which is tuned to the frequency of the control signal. Consequently, signals of frequencies substantially different from the control signal frequency are attenuated by microphone 6.
At the extreme right of FIG. 1 is shown a transformer 60 having a primary winding 61 connected to a standard source of AC. line potential. A low voltage secondary winding 62 is grounded at one terminal and is connected to a rectifier 45 at its other terminal. Rectifier 45 converts the low voltage A.C. into a unidirectional current which is filtered by capacitor 44. The negative direct current potential is indicated by the symbol B- Resistor 37 and capacitor 36 develop a lower potential B- for the low level amplifier stages.
Microphone 6 is coupled to the base 13 of a transistor 1!), which also includes an emitter l1 and collector 12. Resistors 7 and 8 develop operating bias for base 13. The parallel combination of resistor 14 and capacitor 15 is connected between emitter 11 and ground in the usual manner to provide direct current bias for emitter 11 without substantial signal degeneration. A load resistor 9 is connected from B to collector 12. The signal input from microphone 6 is thus amplified by transistor 19 and is coupled via capacitor 16 to the input circuit of transistor 20.
Transistor 20 includes an emitter 21, a collector 22 and a base 23. Resistors 17 and 18 are connected between B and ground and their junction is connected to base 23 to provide proper operating potential therefor. The parallel combination of resistor 25 and capacitor 24 in the emitter circuit of transistor 20 establishes the DC. operatiing potential for emitter 21 and provides signal by-pass.
The amplified signal from transistor 10 is further amplified by transistor 20 and appears across load resistor 19, connected to collector 22. The output signal developed across load resistor 19 is coupled by coupling capacitor 26 to a tap 28 arranged to be moved across a resistance 28. Resistance 28 in conjunction with resistor 27 establishes the operating bias for base 23 of transistor 30. The position of tap 29 on resistance 28 determines the amount of amplified signal coupled to transistor 30.
Transistor 30 also includes an emitter 31 and collector 32. Emitter 31 is connected to ground through the parallel combination of resistor 34 and capacitor 35, which combination performs similarly to its counterparts in the previous stage. Collector 32 is serially connected to B through winding 42 of transformer and resistor 38. A capacitor 41 is connected in parallel with winding 42 and together these elements comprise a tuned circuit which is tuned to the frequency of the control signal. A capacitor 39 is connected between the junction of resistor 38 and winding 42 and ground and serves as a signal by-pass. The unique arrangement of the collector load circuit of transistor 30 comprises the heart of the invention and will be described in more detail below.
Secondary winding 43 of transformer 40 couples the signal developed across winding42 to the base 53 of output transistor 50. A relay winding 47 is connected between B and collector 52 of transistor 50 and a resistor 46 is connected between emitter 51 and ground. The AC. signal impressed across emitter 51 and base 53 is simultaneously rectified and amplified by transistor 50. A large capacitor 48 is connected between collector 52 and ground and serves to delay energization of relay 47 until the control signal has persisted for a predetermined minimum time. When relay 47 has been energized sufficiently it closes its contacts 54, which are coupled to utilization means 55.
The operation of the output circuit of transistor 30 will now be described in detail. This arrangement provides for amplification of control signals lying within a certain amplitude range. For control signals exceeding this amplitude range, the gain of transistor 30 is decreased markedly with increases in the control signal amplitude. This is due to the action of resistor 38 which reduces the supply voltage for transistor 30 in the presence of high amplitude signals. This may be more readily seen by reference to the curve of FIG. 2 in which the input signal voltage to transistor 39 and the voltage appearing across winding 42, which is the output signal voltage of transistor 30, are plotted.
Reference to this curve shows that the output signal voltage increases over a first range of increasing input voltages and subsequently decreases for further increases in input voltage. In other Words, the output versus input curve has a positive slope for a first range of increasing signal and a negative slope for a second range of increasing signal. This results from the fact that the output load current must flow through resistor 38 which develops correspondingly larger voltage drops for increasing signal inputs. Thus, under strong signal conditions, the potential across collector 32 and emitter 31 is reduced, thus causing a corresponding reduction in the gain of this stage. This arrangement provides two types of discriminating actions, namely frequency discrimination and amplitude dis crimination.
The circuit is very effective in rejecting spurious noise signals by virtue of this novel action of stage 30. The noise immunity of this circuit is further enhanced since microphone 6, which it Will be recalled is tuned, provides a measure of frequency discrimination and capacitor 48 provides discrimination based upon the duration of the signal.
The excellent noise immunity of this circuit is obtainable since the nature of probable noise impulses is fairly Well known, and consequently, the circuit may be tailored to reject these noise impulses. For instance, noise generally comprises impulses of short duration over a wide frequency range. These impulses are usually much larger in amplitude than the maximum control signal amplitudes encountered. Consequently, microphone 6 and tuned circuit 41-42 discriminate against the noise impulses on the basis of frequency. The main advantage of the invention is that resistor 38 adds amplitude discrimination to insure that signals exceeding a predetermined maximum amplitude are substantially eliminated from the output of transistor 30.
While circuits of the prior art have utilized limiter arrangements to limit the maximum signal output amplitude, the circuit of the invention actually results in a decrease in the signal output amplitude for signals exceeding a predetermined maximum.
In the circuit a relay 47 is shown as the device for controlling utilization means 55. It should be obvious to those skilled in the art that relay 47 could be replaced by other devices such as a DC. motor.
What has been described is a novel remote control unit which is compact, economical and relatively immune from spurious actuation. The invention has been described in its preferred form of construction, but it will be appreciated that numerous changes and modifications may be made therein without departing from its true spirit and scope as set forth in the following claims.
What is claimed is:
l. A control system responsive to remotely transmitted ultrasonic control signals of particular frequency and predetermined minimum amplitude and duration comprising; receiving means for receiving and converting said control signals into corresponding electrical signals; and amplifying means including an electron valve for amplifying said electrical signals; supply means supplying energy to said valve, said supply means including a relatively large resistance for providing said electron valve with a characteristic such that its output is decreased with increasing signal amplitude for all signals having amplitudes greater than a predetermined level, whereby said system translates substantially only signals lying within a restricted amplitude range.
2. A control system for energizing a utilization device responsive to remotely transmitted ultrasonic control sig nals of particular frequency and predetermined minimum amplitude and duration comprising; receiving means for receiving and converting said control signals into corresponding electrical signals; amplifying means including a transistor for amplifying said electrical signals; means coupled to said amplifying means for energizing said utilization device only responsive to signals having at least said minimum duration; said amplifying means including a tuned circuit tuned to said particular frequency and a large resistance in the energizing circuit for said amplifying means, said amplifying means being thus arranged such that its output is decreased with increasing signal amplitude for all signals of substantially said frequency having amplitudes above a predetermined level, whereby signals other than said signals of said particular frequency and lying Within a restricted amplitude range are substantially rejected by said control system.
3. A control system adapted to energize a utilization device responsive to receipt and translation of an ultrasonic control signal of particular frequency and predeermined minimum amplitude and duration comprising; receiving means including tuned means for accepting signals, including said control signal, within a narrow frequency band; means for converting received signals into corresponding electrical signals; amplifying means, responsive substantially only to signals of said particular frequency, for amplifying said electrical signals; means for detecting the amplified signals; and means for energizing said utilization device responsive to detection of signals having said predetermined minimum duration; said amplifying means including a transistor having an input circuit coupled to said means for converting and an output circuit coupled to said means for detecting, said output circuit including a relatively large resistance for re- (racing the voltage available for said transistor under strong signal input conditions, whereby the gain of said transistor is decreased for all signals having amplitudes exceeding a particular level.
4. A control system adapted to energize a utilization device responsive to receipt and translation of an ultrasonic control signal of particular frequency and predetermined minimum amplitude and duration comprising; receiving means including tuned means for accepting signals, including said control signal, within a narrow frequency band; means for converting received signals into corresponding electrical signals; amplifying means, responsive substantially only to signals of said particular frequency, for amplifying said electrical signals; means for detecting the amplified signals; and means for energizing said utilization device responsive to detection of signals having said predetermined minimum duration; said amplifying means including a transistor having an input circuit coupled to said means for converting and an output circuit coupled to said means for detecting, said output circuit including a relatively large resistance for reducing the voltage available for said transistor under strong signal input conditions, whereby said transistor has an output versus input curve characterized by a posi tive slope over a first range of increasing signal levels and by a negative slope over a subsequent range of increasing signal levels.
5. A remote control system comprising; means for transmitting an ultrasonic control signal of particular frequency and predetermined minimum duration and amplitude; translation means including means for receiving and converting said ultrasonic control signal into a corresponding electrical signal and means for amplifying said electrical signal; means for energizing a utilization device responsive to translation of a signal having said predetermined minimum amplitude and duration; and discriminating means interposed between said translation means and said means for energizing; said discriminating means including an electron valve having an output circuit comprising a serially connected tuned portion and a resistive portion, said tuned portion responding to signals of said particular frequency and said resistive portion determining the gain of said electron valve as a function of the signal input amplitude, whereby for a first range of increasing signal amplitudes the output of said valve increases and for a subsequent range of increasing signal amplitudes the output of said valve decreases 6. A remote control system comprising; means for transmitting an ultrasonic control signal of particular frequency and predetermined minimum duration and amplitude; translation means including means for receiving and converting said ultrasonic control signal into a corresponding electrical signal and means for amplifying said electrical signal; means for energizing a utilization device responsive to translation of a signal having said predetermined minimum amplitude and duration; and discriminating means interposed between said means for amplifying and said means for energizing; said discriminating means including a signal translation element hav- References Cited by the Examiner UNITED STATES PATENTS 2,215,946 9/40 Von Radinger 325473 2,345,472 3/44 Goldsmith 343225 2,809,240 10/57 Freedman 33031 2,907,012 9/59 Pitman 340169 3,027,497 3/62 Carlson et al. 3171.47 3,050,661 8/62 Jenkins 340-171 3,052,853 9/62 Smith 33029 3,056,928 10/62 Marks 317l47 OTHER REFERENCES Kruse- The Noise Reduction Problem: Radio, April 1936, No. 208, pp. 44-45.
NEIL C, READ, Primary Examiner,
WILLIAM C. COOPER, Examiner.