Abstract: A look-up table for use in a bridge employing negative filtering for interconnecting first and second networks in a data communications system. Associated with each data transmission is a source and destination address each having a total of (m+n) binary data bits, the bridge passing the data transmission from one network to the other unless the destination address is found in the look-up table and corresponds to the sending network. The look-up table comprises an encoding means responsive to an (m+n) bit address for producing first and second codes having respectively m and n bits of data which together allow the (m+n) bit address to be decoded unambiguously, a random access memory (RAM) coupled to the encoding means and having m addressable locations each for storing at least n bits of data, and a contents addressable memory (CAM) coupled to the encoding means and having a plurality of addressable locations each for storing at least (m+n) bits of data.

Abstract: A unipolar pulse communication system exploits the fact that certain computer terminals will react only to information pulses of a specific polarity and remain passive to pulses of the reverse polarity. A device at one end of the system passes pulses unchanged, from a first station of a computer to a single cable at the output of the device. Pulses received from a second station of the computer pass through the same device but are inverted before being passed through to the same cable. At the other end of the cable, all pulses are passed unchanged to a third station, and all pulses are inverted and then passed through to a fourth station. As the third and fourth stations only react to information pulses of a specific polarity, the result of the device is to permit two stations of the computer to be connected to two remote stations using only a single interconnecting cable. The device at either end of the cable may be designed so as to permit the same device to be used at either end of the cable.