The MC34216A is developed for use in telephone applications where,
besides the standard telephone functions, the group listening–in feature is
also required. In cooperation with a microcontroller, the circuit performs all
basic telephone functions including DTMF generation and pulse–dialing.
The listening–in part includes a loudspeaker amplifier, an anti–howling
circuit and a strong supply. In combination with the TCA3385, the ringing is
performed via the loudspeaker.