The PCM/ECM and the SMARTRA communicate by dedicated line.

During this communication of PCM/ECM and SMARTRA, the K line of PCM/ECM cannot be used for communication.

The PCM/ECM controls the communication either to SMARTRA or to other devices(e.g. scanner) on K line by switching of a multiplexer and specific communication procedures.

The multiplexer is a part of PCM/ECM H/W.