454,564. Exchange systems. MASTINI, D., 251, Corso Vittorio Emanuele, Rome. April 1, 1935, No. 10097. [Class 40 (iv)] [See also Group XL] Telephone subscribers are provided with apparatus whereby they may communicate with any other subscriber through the exchange network with the aid of portable wireless apparatus when they are away from their substations. As shown, the removal of the instrument at the portable set shown on the left of the Figure switches on the transmitter Tm and the reception of the resulting signal by the circuit RF at the substation produces a voltage for biassing the speech amplifier BF and energizes a relay A which energizes a relay B so that the telephone set is disconnected and the line is bridged over a repeating contact and associated with the wireless apparatus.; Impulses dialled at Z are repeated by A to the exchange at which the call is established in known manner. A call from the exchange energizes a relay E which switches on the transmitter Tf and makes a circuit for a self interrupting relay V to cause buzzer-modulated carrier wave to be sent out. E locks up and energizes a thermal relay T.C., which in due course shunts the locking circuit. When the portable station answers the call, the consequent switching on of the transmitter Tm causes the actuation at the substation of relays A, B which complete the circuits described above.