A system for automatically addressing serially connected slave devices, the system comprising: a master device including a serial communication transceiver ; multiple slave devices , each slave device including a serial communication transceiver , an address input port , an address output port , and a controller (208A, 208B 208C), the controller (208A, 208B 208C) in communication with the serial communication transceiver , the address input port and the address output port ; a serial communication wiring bus connected between the serial communication transceiver of the master device and the serial communication transceivers of the multiple slave devices ; and at least one digital address line connected between the address input ports and the address output ports of the multiple slave devices in a daisy chain arrangement, characterised in that each controller (208A, 208B 208C) is configured to: receive a pulse-width modulation (PWM) or pulse-frequency modulation (PFM) signal from a previous one of the multiple slave devices in the daisy chain arrangement via the address input port , the pulse-width modulation (PWM) or pulse-frequency modulation (PFM) signal corresponding to an address of the previous one of the multiple slave devices in the daisy chain arrangement; determine an address for the slave device comprising said controller according to the received PWM or PFM signal; and transmit a PWM or PFM signal to a subsequent one of the multiple slave devices in the daisy chain arrangement via the address output port , the transmitted PWM or PFM signal indicative of the determined address for the slave device comprising said controller and different than the received PWM or PFM signal; wherein the master device is configured to transmit a save command to at least one of the slave devices via the serial communication wiring bus to lock the address determined by the at least one slave device. a master device including a serial communication transceiver ; multiple slave devices , each slave device including a serial communication transceiver , an address input port , an address output port , and a controller (208A, 208B 208C), the controller (208A, 208B 208C) in communication with the serial communication transceiver , the address input port and the address output port ; a serial communication wiring bus connected between the serial communication transceiver of the master device and the serial communication transceivers of the multiple slave devices ; and at least one digital address line connected between the address input ports and the address output ports of the multiple slave devices in a daisy chain arrangement, characterised in that each controller (208A, 208B 208C) is configured to: receive a pulse-width modulation (PWM) or pulse-frequency modulation (PFM) signal from a previous one of the multiple slave devices in the daisy chain arrangement via the address input port , the pulse-width modulation (PWM) or pulse-frequency modulation (PFM) signal corresponding to an address of the previous one of the multiple slave devices in the daisy chain arrangement; determine an address for the slave device comprising said controller according to the received PWM or PFM signal; and transmit a PWM or PFM signal to a subsequent one of the multiple slave devices in the daisy chain arrangement via the address output port , the transmitted PWM or PFM signal indicative of the determined address for the slave device comprising said controller and different than the received PWM or PFM signal; wherein the master device is configured to transmit a save command to at least one of the slave devices via the serial communication wiring bus to lock the address determined by the at least one slave device. <EOS>