Question:  I need to connect two separate single channel Clear-Com party-line systems in separate buildings together.  The buildings have both fiber cable and CAT-5 runs between the buildings, can I connect the two PL systems together via one of these transmission mediums?
Answer:  The EF-701M Interface converts a channel of standard or TW party line to 4-wire audio and, at the same time, converts a DC-voltage call signal or 20-kHz call signal to RS-422 data. This 4-wire audio and RS-422 data can then be sent to a fiber-optic converter (modem); over copper, unshielded twisted-pair (UTP) cable such as Category 3, 5, or above; or it can simply be used as an excellent stand alone 2-wire to 4-wire converter. In most cases though, EF-701M units will be used in pairs, because once the signal is converted to go over the chosen transmission medium, it must be reconverted to 2-wire mode to properly connect to the party-line system or station at the other end of the line.
The EF-701M obtains its DC operating current from the local party-line connection on pin 2 of the XLR connector. This current is not conducted between EF-701M units, so each EF-701M must be powered by an intercom line as shown in the diagram below:







NOTE:  If the decision to use fiber is employed the Clear-Com FIM-202 can be used as a 4-wire to Fiber interface at each end of the EF-701M.