Abstract: A device for interrupting the siren signal when the transmit microphone is keyed on a radio communication and siren system. Keying the microphone energizes the coil of a relay, opening a first set of contacts which had formed a complete circuit from the siren signal output source to the siren speaker, so that during voice transmission over the microphone the siren signal is silenced. The siren signal is diverted through a second set of contacts into a set of resistors. Unkeying the microphone de-energizes the relay coil, opening the second set of contacts and closing the first set of contacts, thereby recreating the complete circuit to the speaker and allowing the speaker to emit the siren sound.