Single two-wire telephone system for trains - has subscriber terminals on train acting as bidirectional signal regenerators in two bands

摘要

The telephone system, for trains, allows the exchange of information between subscriber terminals aboard the train via a single two-wire circuit. The information is transmitted as packets in the forwards and backwards directions between the locomotive (1) and carriages (2) using different frequency bands. The subscriber terminals are connected in series into the two-wire circuit and act as regenerators for information packets that are not addressed to them (those addresses to them are received and not passed on). The regeneration and reception from one direction takes place in one frequency band, and the regeneration and reception from the other direction takes place in a second frequency band.