503,498. Exchange and direct-call systems. SHIPTON, E. Oct. 6, 1937, No. 26988. [Class 40 (iv)] Operation of a key at a.telephone substation causes incoming calls to operate a relay which controls visible or audible signals or both at various parts of the building and extends the telephone line to a circuit over which a reply signal is given either automatically (e.g. by a gramophone or buzzer). or by an attendant. In an arrangement for a direct-call intercommunication system, Fig. 1 (not shown), the key removes a short-circuit from the relay which is thus enabled to pull up in response to the calling signal. In the exchange sub-station shown, the key energizes a relay R which connects the upper winding of relay T to the telephone line. On the arrival, of a call, T locks over its lower winding, connects the line to circuit 22, 23 and lights characteristic lamps 25a, 25b at the substation and elsewhere. The relay is unlocked at 20 by an attendant, or by the release of R by the subscriber, or otherwise from the indicating lamps. In a modification the relay may complete a conference circuit and transmit a code signal over a separate ringing circuit.