The bus connection module acts as an interfacing unit between a SPACOM device and the fibre-optic SPA bus. The bus connection module converts incoming optical signals from the SPA bus to electrical RS485 or SPA (+5 V) signals for the SPACOM devices and vice versa. The bus connection module is plugged rear plate of the host device. The bus connection module SPA-ZC21 can be used in combination with any SPACOM device provided with a 9-pin D-type connector. Further, by means of a set of optional mounting accessories the bus connection module can be connected to a SACO data communication and reporting unit.