These devices are dual phaselocked loop (PLL) frequency synthesizers in tended for use primarily in 46/49 MHz cordless phones with up to 10 channels. These parts contain two maskprogrammable counter ROMs for receive and transmit loops with two independent phase detect circuits. A common reference oscillator and reference divider are shared by the receive and transmit circuits. Frequency selection is accomplished via a 4bit parallel input for the MC145166. The MC145167 utilizes a serial interface. Other features include a lock detect circuit for the transmit loop, illegal code default, and a 5 kHz tone output.