Universal differential duplex telegraph set

This apparatus can be used either as a terminal set, or two of them in combination can be used to form a repeater. The apparatus is rack-mounted and wired in the factory so that a minimum of connecting up has to be done in the telegraph office itself. A panel can be used as a duplex terminal in the ordinary way, or as a "half duplex" set by effecting a mere switching operation. As a half duplex set, the usual sending and receivings legs are brought to the panel and the duplex apparatus effects the translation of the double current signals from the main line to the open-circuit (single-current) signals for the local circuit, and vice versa. The balancing equipment is somewhat novel in its arrangement.