The MX014 Voice Band Inverter gives the security of private voice communications to land mobile radio users, as well as to the users of other shared radio channel systems. Designed for use in half-duplex systems, the MX014 exchanges high and low frequencies in the voiceband and renders transmitted messages unintelligible. This privacy function is achieved by a single frequency inversion. When used with CTCSS, PvtSQUELCHTM privacy adapter operation is achieved. Sharp cut-off in the internal voiceband filters permits operation with CTCSS and similar sub-audio signaling schemes. This results in high quality recovered audio. The core of the MX014 consists of two audio band pass filters and a balanced modulator. The device uses a programmable clock divider which controls the carrier and filter cut-off frequencies. Control of the RX/TX, PTL and privacy function is by pin selection. The MX014 operates from a single 5V supply and uses a 4 MHz crystal oscillator to ensure the correct pitch in recovered speech. Signal coupling and decoupling are the only external components needed. The device is available in 24-pin PLCC (MX014LH), 24-pin PDIP (MX014P) and 24-pin CDIP (MX014J) packages.