The block diagram in Figure 1 shows an intercom system with an internal and external unit. The two-wire analog interface connects the two units in point-to-point fashion. An additional external switch is required to connect several parties in multiple intercom systems.

The hybrid circuit can also be extended to enable communication via phone network with remote stations – for example, in alarm systems.
The speakers are connected directly to the Class-D amplifier output, while the analog microphone is connected to the microphone input. Microphone amplification can be programmed internally in 10dB increments.
Thanks to an internal acoustic echo canceller, together with line echo cancellation and active noise suppression via the DSP, excellent speach quality is assured.

The EEPROM contains the firmware for the CX20662, and several GPIOs are available to perform a number of different functions. For example, the GPIOs can be directly connected to pushbuttons or be controlled via a microcontroller, to enable such functionality as microphone and speaker muting, or volume control.
CONEXANT supplies the complete circuit diagrams, including the hybrid circuit which is directly connected to the CX20662’s 2-wire interface.
Sounds interesting? Then please don’t hesitate to call CODICO!
Richard Schildberg, Tel.: +49 8233 795 304 A03