The CMX138A operates in half duplex, so whilst in receive mode the transmit path (microphone input and modulator output amplifiers) can be disabled and powered down. The audio output signal level is equalised (to VBIAS) before switching between the audio port and the modulator ports, to minimise unwanted audible transients. In the powersave state, the audio output pin enters a hi-Z state, however, if left enabled and the preceding stages powersaved, it will be driven to the VBIAS level.