A master-slave communication system for a communication switch is provided. The system comprises a master controller generating commands and receiving status signals and slave devices associated with the master controller. Each slave receives commands, executes local commands responsive to the commands and generates status signals for the master controller. Each slave has a communication arrangement for signals transmitted between it and the master controller. The arrangement comprises a communication controller associated with the master controller. The communication controller receives commands, transmits commands to each slave, receives status signals and provides information relating to the status signals to the master controller; also the controller has a communication link which transmits commands to each slave and the status signals to the controller. The system allows local commands executed by the slaves to replace other commands directed by the master controller to the slave. Further, each slave communicates independently with the master controller.