Manually keyed pulse transmitter

Claim 1

A signalling device comprising a plurality of signal generating switches, a plurality of detecting circuits for detecting the operation of said switches, each including an amplifier corresponding to a respective one of said switches and an integrating circuit connected to the output of said amplifier, a plurality of pulse forming circuits corresponding to a respective one of said detecting circuits each including a differentiating circuit being connected to the output of said integrating circuit and producing output pulses having a pulse width shorter than the interval of operation of said signal generating switches in response to signals detected by said detecting circuits, an encoder for encoding the output pulse signals from said pulse forming circuits and applying to a receiving device said encoded signals from a signal generating switch even while one or more other signaL generating switches are maintained in their operative state, an OR circuit connected to receive said output pulse signals or said encoded signals, a delay circuit connected to delay the output signal from the OR circuit a predetermined time, a first AND circuit connected to receive the output signal from the delay circuit, a pulse generating circuit responsive to the output signal from said first AND circuit for generating a synchronizing signal, a time emitter circuit connected between an output terminal of said pulse generating circuit and an input terminal of said first AND circuit to control said pulse generating circuit such that until a predetermined time interval elapses after generation of one synchronizing signal, the generation of the next succeeding synchronizing signal is prevented and means to apply said synchronizing signal to said receiving device to control the reception of said encoded signals.