The SPACOM devices, e.g. the relays and the
annunciator units are connected to the fibreoptical SPA bus by means of bus connection
modules. The bus connection module SPAZC22 converts the optical signals of the SPA bus
to RS 485, SPA (+5 V) or RS 232 signals and
vice versa. The bus connection module is
provided with a built-in power unit allowing the
SPACOM device to be disconnected from the
bus connection module, for instance, for service
without interrupting the data communication
over the optical loop.
The bus connection module is provided with
one 9-pin D type subminiature connector for
RS 485 or SPA connections, one 25-pin D type
connector for RS 232 connections and, according
to order, two or five opto-connector couples for
fibre-optical cables. The fibre-optical links can
be based on glass fibre cables, plastic core cables
or both types mixed.
The bus connection module is mounted in a
suitable place in the apparatus cabinet and the
connection cable of the module is plugged to the
D-type connector on the rear panel of the
SPACOM device. The bus connection module
type SPA-ZC22 connects to any SPACOM
device provided with a D-type connector. The
bus connection module can also be connected to
the master units, such as substation level units

SACO 148D4 and SRIO 1000M, of the communication system.