Circuit arrangement for balancing a two wire full duplex data transmission system

In a two wire, full duplex data transmission system wherein a transmitter and receiver in one station are connected by two wires to a transmitter and receiver in another station, the transmitter in each station being connected by means of a balancing apparatus to the receiver therein for adjusting the value of the current from the transmitter flowing through said two wires to the receiver in the same station to be equal to current flowing from the transmitter directly to the receiver in said another station, the balancing apparatus comprising.

• a plurality of parallel-connected current paths, each comprising a series combination of a time stage and an amplitude stage,
• said parallel-connected current paths being connected to received current from the transmitter in the same station, a plurality of subsidiary currents flowing through said parallel current paths to a common output terminal which couples a sum current of said subsidiary currents to the receiver in the same station,
• each said time stage being constructed to produce predetermined, but different, timing signals in relation to a data signal being transmitted from the station, said amplitude stages being constructed to adjust the values of said subsidiary currents flowing therethrough and said time and amplitude stages having a connected relationship such that each said amplitude stage is effective for a duration determined by the timing signal from the associated time stage.