GB320366A - Improvements in automatic telephone systems - Google Patents

Abstract

320,366. Betulander, G. A. July 10, 1928. Automatic exchange systems. - In a cross - bar switch which serves as a 100-point group selector or connector, the primary magnets ANV operate successively in response to an incoming train of impulses, and then the secondary magnets ANS operate either automatically or in response to a further impulse train to close the contact-sets of the selected group in turn until an idle trunk is found or the wanted line is reached. Each magnet on energization disconnects the preceding one, but in order to prevent two lines or trunks being connected during the successive operation of the magnets ANS, the wires leading to the odd and even contact-sets are multipled together separately. Once the required connection has been made, the contact-set is held operated by the secondary magnet ANS alone, the primary magnet ANV being released. Specification 13524/14 is referred to. Group selector, Fig. 1. Relay AR energizes over test wire LIII, and impulses are received over wire LII. The first impulse energizes magnet ANVO, which locks in series with relay IVRI, and parallel relay SMR, which remains operated throughout the train. At the second impulse, magnet ANV1 energizes and locks over relay IVR2, which disconnects magnet ANVO and relay IVR1. Relay HIVR pulls up. At the third impulse, magnet ANV2 energizes and locks over relay IVR1, which releases magnet ANV1 and relays IVR2, HIVR. This action continues until the end of the train, relay IVR1 energizing for the odd impulses, and relays IVR2, HIVR for the even impulses. Parallel relay SMR then falls back, and magnet ANS1 energizes, operating the first contact-set in the selected group. Test relav SR now connected to the test wire of the outgoing trunk is inoperative if it is busy, and magnets ANS2, ANS3, &c. energize in turn until an idle trunk is reached, each magnet disconnecting the previous one, when relay SR pulls up and opens the circuit for the next magnet. Switching relay ALR energizes, locks in series with the operated secondary magnet ANS, disconnects the operated primary magnet ANV, and connects in the high resistance winding of relay AR to decrease the holding current. Connector, Fig. 2. Relay AR energizes over test wire LIII, and the first train of impulses operate magnets ANV in turn as in the group selector. When parallel relay SMR falls back, change-over relay SVR energizes over its upper winding, closes a locking circuit through its lower winding and the operated magnet ANV, and transfers the control wires to magnets ANS, which are operated in turn by the final train of impulses until the desired contact-set is operated. When relay SMR falls back, test and switching relay LYR is connected to the test wire of the wanted subscriber and energizes if the line is free and completes the connection, the operated secondary magnet ANS being locked in series with relay IVR1 or IVR2, and the operated primary magnet ANV being released.