Abstract:
A radio operated remote control unit for attachment to a transmitter and having a second module attached to a transreceiver, which, through the use of a dual tone multi frequency signal, turns on the lights, or similar work, and maintains that status for a predetermined period of time. Also the electrical circuit employed to accomplish the said work.

Description:
BACKGROUND OF THE INVENTION 
     Many private airplanes are being flown throughout the country, which are being housed in private hangers on small airfields, which close early at night. This presents a serious problem to planes seeking to land after dark. Arrangements must be made with the field to have personnel on duty after hours. Often delays occurs that make this impossible and gives rise to dangerous situations. It is an object of this invention to provide a means having one attachment on the aircraft and the other on the transceiver at the control tower of an airfield, which, when activated, turns on the lights at the field, even though the attendants are no longer there. 
     SUMMARY OF THE INVENTION 
     A device having two parts, one attached to the transmitting apparatus of an aircraft radio, and the other to the transceiver in the control tower of an airport, enabling the pilot of the aircraft, through a novel circuit transmitter attachment and in the transceiver attachment, to turn on the lights at the airport for a preselected period of time, enabling the pilot to land the plane unassisted by ground personnel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic sketch of the electrical circuits employed to accomplish the desired transmission and reception of a signal and the activation of the work. 
     FIG. 2 is a diagrammatic sketch of the circuit employed in transmission of the signal. 
     FIG. 3 is a continuation of the diagrammatic sketch from FIG. 2, illustrating the circuits employed in the receiver. 
     FIG. 4 is an elevational view of the front and an elevational view of the rear of the aircraft module housing. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The device is contained in two modules, the module 1 being located in the aircraft, where it is connected into the transmitter (not shown) through the conduit 3 and which has a socket to receive the microphone conduit 4. A battery is mounted in the module 1 and has the door 5 for access thereto formed in said module 1. A push button S1 closes the switch and energizes a relay K2, closing contact A and supplying voltage from the battery B1 to the resistor 44 and diode D11, which supplies the current voltage for the tone generator IcI3. The contact B is also closed, taking the input of the transmitter in the module 1 away from the microphone 6 and connects it into the output of ICI3. The exact output level is determined by R46, R47 and R48, which should be adjusted for approximately 90% modulation. The contacts C will be moved to closed position to transmit the tones to be generated. The capacitor C31 keeps the relays K2 energized for approximately one second, permitting the operator to merely press button S1, without having to hold it in pressed position. 
     An audio sample from the control tower receiver is fed initially to four stages of programable level adjustment. The first two stages, R35 through R38, both inclusive, are 6dB attenuators, and the second two, IC4C, IC4D and R39 through R42, both inclusive are 6dB amplifiers. Normally, these four stages will be by-passed by attaching jumping wires (not shown) to the appropriate terminals, however, should the output of the receiver be too great or too small, these stages can be used to adjust it. 
     The next stages are active filters formed by IC1 and IC2, whch are high pass and low pass, respectively, and their associated resistors R1 through R16 and capacitors C1 through C16. The output of these filters are sine waves which will be converted to square waves by IC3 and diodes D1 through D8. After squaring, the signals are amplified to TTL-compatible levels by IC4A and IC4B, then fed into IC5A through IC5D to further condition the signals for introduction to the decoder IC6. When the decoder IC6 detects a valid input signal, it provides the binary-coded digit (in this case, the number 5) and a strobe signal which verifies a valid input. When all is correct, the output of IC7C will change momentarily, about one second which sets a latch formed by IC9A and IC9B. The output of IC9A will go high, which causes transistor Q1 to conduct, and relay K1 to energize. The contacts 8, 9 of K1 activate the AC contactor K3 which actuates the switch 6,7 and turns on the lights. At the same time, the output of IC9A causes IC10 to oscillate at a rate determined by the potentiometer R31. IC11 is a frequency divider. After 16,384 cycles of oscillation of IC10, Ic11 signals IC12 which is a monostable multivibrator, which provides a pulse of approximately 600 microseconds. This pulse resets the latch IC9A and IC9B, and clear the counter IC11 through IC9C. When the latch resets, Q1 stops conducting and K1 relaxes, turning off the lights. Varying R31 will change the frequency of IC10 such that there will be ten to twenty minutes of light at each use. Now IC11 is ready for the next actuation. In the event that a second valid signal is detected before the lights go off, the pulse from IC7C which sets the latch is also fed through IC9C to IC11. In this way, IC10 continues to oscillate, but IC11 is forced to start counting from zero, thus giving the second pilot the same ten to twenty minutes of light without waiting for the lights to go off and without the danger of the lights going off when they are needed most. 
     A manual override switch S2 is provided for such occasions upon which continuous lighting is required. Said Switch S2, when manually actuated, will cause the lights to remain on until the switch is again opened. 
     It is contemplated that multiple signals for multiple purposes may be accomplished through this system by adding a keyboard to IC13 and maintaining a constant supply of power thereto. This would permit multiple tone generations, each pair of tones accomplishing a given act.