A system for controlling operation of a clay pigeon launcher in response to a voice command, to one of a plurality of microphones. The system provides for the averaging of the signal output of the microphones and the selection of the output of highest level. These outputs are compared and if the highest level is greater than a predetermined magnitude provides an operating signal for the launcher.

Means and method of reducing the probability of false indications of microphone activity in a multimicrophone system incorporating means for sensing the activity of microphones. The microphone, which is truly active, will receive its signal from its user before any of the other microphones receive the signal. The microphone circuit then sends a control wave to all of the other microphone channels reducing their amplifier's sensitivity and making them insensitive to false indication of activity.

A voice-actuated switching system selectively connects multiple microphones to an audio line in accordance with the output signal levels from each of the microphones. The state of each microphone is determined by its use and can exit in one of three states: selected, mixed, or off. The microphone with the greatest output signal level at any given time is considered in the selected state and is selected for connecting to the audio line with no loss. Those microphones in the mixed state have their output signal levels attenuated before being connected to the audio line. And those microphones in the off state have their outputs essentially disconnected from the audio line. The user of a microphone while in the mixed state can be heard along with the user of a microphone while in the selected state although at a lower level. Improved accuracy is obtained in the microphone selection process by comparing the microphone signals to each other and to a reference level that takes into account any offsets induced into the signals by the system. The system can accommodate any number of microphones.

Control apparatus is provided to intercommunicate transmit-receive systems such as radio sets one with another or with a telephone network. First and second signal processors convert a signal input from either of the systems into a form capable of energizing a switch which, in turn, closes a relay coupling the input from one system into the other. Also, the circuit for applying the incoming signal to either one of the signal processors, such as the first processor, includes a normally-closed relay of the switch of the other processor, i.e., the second processor. Therefore, intercommunication is voice-operated since and incoming audio signal transmitted into either system activates a switch of that system to communicate its transmitting system with the other. Activation of that switch utilizes the normally-closed relay of the other switch. Return transmissions are handled in a reverse but otherwise is identical manner.

A telephone conference system includes a conference bridge for coupling multiple conference ports associated with corresponding conference stations. The bridge includes means for summing incoming signals from all the conference ports and supplying the summed signals to all the conference ports. A differential amplifier is connected to each of the conference ports and differentially receives (1) incoming signals at the corresponding conference port and (2) the output of the summing means so as to cancel from the output of the summing means any signal received by the summing means from the corresponding conference port. Thus, the differential amplifier passes only that portion of the output of the summing means that is received from conference ports other than the particular port to which that differential amplifier is connected. A voice actuated switch is connected to each conference port for controlling the transmission of incoming audio signals to the respective ports, and the number of switches that can be closed at the same time is limited to a preselected maximum, while permitting the continuous transmission of outgoing audio signals from all the ports regardless of which switches are open or closed.