Anti-blocking device including stuck microphone reliever for aircraft voice communication system

摘要

Systems for preventing channel blockage on aircraft voice communication frequencies caused either by a pilot beginning a transmission while someone else is transmitting on the same channel (i.e., "stepping on" or "blocking" the first transmission), or by a "stuck microphone" condition resulting from undesired activation of the microphone switch circuit. In accordance with the invention, a "step-off" device (SOD) and a "stuck microphone reliever" (SMR) are combined in a single device, termed an "anti-blocking device" (ABD). The entire device may be provided in retrofit form and draws all its operating power from the radio push-to-talk switch line, with no internal modification to the radio required. The step-off device portion of the anti-blocking device senses when a selected radio frequency is in use, and when in use, prevents transmission even when the microphone switch circuit is operated. The stuck microphone reliever includes a transmitter-disabling means connected to the microphone switch circuit for limiting any transmission to a predetermined duration even though the microphone switch circuit is activated for a longer duration.