A reduced size multiplexer and, in particular, a reduced size optical signal multiplexer module is provided for use in a reduced size enclosure. The optical signal multiplexer module has electrical and optical connectors on its faceplate to provide ease in access without having to remove the optical signal multiplexer from the enclosure. The optical signal multiplexer circuit is configured in a standard Type 400 mechanics circuit board arrangement. The optical signal multiplexer module therefore can be inserted into an enclosure in a direction opposite to that in which the DS1 or DS3 connector projects from the face plate, so that the DS1 or DS3 connector remains freely accessible outside of the enclosure when the optical signal multiplexer module is fully loaded into the enclosure. DS1 and DS3 cables and optical fibers can thus be easily coupled to the DS1 and DS3 and optical connectors, respectively, when the SONET multiplexer circuit is fully loaded into the enclosure.