Abstract: A family of improved 2-wire resistance bridges having from 3 to 14 ports, or legs, is provided for use in interconnecting a plurality of stations or devices in a private line circuit. The bridges include a resistance connected in shunt across the common end of each leg in the bridge, which permits the intrinsic port-to-port loss of the bridges to be adjusted to a desired value that essentially equals the difference between standard toll line input and output power levels, while at the same time maintaining the proper terminating impedance for each of the interconnected devices.

Abstract: A 4-wire, 8-leg resistance bridge for interconnecting up to eight stations in a full conference system includes a two line input port and an associated two line output port for each of eight 4-wire telecommunication transmission lines. By providing a certain pattern of straight and rollover (reverse) connections between various pairs of the lines in the bridge, an essentially infinite return loss between the input and output ports of each leg is achieved. In addition, the bridge has a uniform natural loss between each leg's input port and the output ports of the other legs, and provides the proper terminating impedance for each of the interconnected transmission lines.

Abstract: An interface unit for interconnecting data terminals and data sets in a serial binary data communication system. The unit includes a plurality of standard multipin connectors, one for each data device being interconnected. Binary signals received at the data input pin of any connector are transmitted to the data output pins of each other connectors simultaneously. A return copy option is provided whereby signals received at a connector's input pin are also transmitted to its output pin. The disclosed device provides an essentially transparent interface between multiple data terminals and data sets at transmission rates up to at least 9600 baud.