The ComNet FDC10 Series bi-directional contact closure transceiver provides bi-directional transmission of contact closure over one multimode or single mode optical fiber. The transceiver has a contact input and a 0.5 amp contact output. The bi-directional contact closure module has two relay outputs and one relay input. One relay output follows the "relay input" at the remote end. When the remote "relay input" is shorted, the local relay output is closed and vice-versa. The second relay output is closed when "carrier" is detected from the remote end, this indicates that the optical fiber is connected and that the remote end has power and is operating.