Patent GB-191309169-A (GB)
Title: Improvements in Telephone Exchanges.
Filed: 1913-04-18
Granted: 1913-11-20
Abstract: 9169. Siemens Bros. & Co., [Siemens & Halske Akt.-Ges.]. April 18. Semi-automatic exchange systems.-In systems for establishing calls over junction lines between manual and automatic exchanges, the B-operator at the automatic exchange, who sets the selectors on the line of the wanted subscriber, is enabled to communicate over the junction line with the calling subscriber by the operation of a key, at the same time stopping the operations which normally take place automatically after the operation of her impulse-sender. In the system shown, a calling line is connected by a pre-selector VW to an idle cord-circuit, and the A-operator, on the depression of her order-wire key DT, is connected by a selector DW to an idle order wire DL. The B-operator's service selector VLW is in connexion with a pre-selected idle junction, the number of which is indicated by the lamp 14. The B-operator tells the A-operator which junction to use, and operates her impulsesender V to select the wanted line. At any time prior to the disconnexion of the impulsesender, the B-operator can communicate with the calling line over the junction by depressing her key BT. The operation, in fuller detail, is described below. Connexion of calling line to idle cord-circuit. The pre-selector VW is rotated under the control of the line relay R and test relay T in the usual way to find an idle cord, when the relay T energizes over a cord contact 27. A line relay R1 closes the circuit of the calling lamp AL, and closes contact 37 to maintain the circuit of the relay T when the plug is lifted. Connexion of A-operator to idle order wire DL. The operator connects her speaking set A to the calling line by depressing the key 9, learns the connexion required, and then depresses her order-wire key DT, thus energizing the motor magnet D1, which rotates the selector DW until the relay T<1> energizes over the contact I of a free order-wire. Selection of wanted line by B-operator. The service selector VLW normally connects the B-operator's impulse-sender V to a pre-selected idle junction, the number of which is indicated by the lamp 14. She informs the A-operator which junction to use, and then sets her impulse-sender, thereby (1) opening contact I so as to render her order wire busy, (2) opening contact II to prevent movement of the service selector, (3) closing contact III to energize a relay T2, which opens contacts 17, 18 in the junction circuit to prevent the selecting- impulses passing back over the calling line, and (4) connecting the impulse-sender V to the selector trunk a, b. The selectors are operated in the usual manner. Disconnexion of impulse-sender &c. When the A-operator inserts the plug 19 in the jack 20, the relay C opens the circuit of lamp 14 at contact 22, and prepares at contact 23 a circuit for the test relay P, which is completed at contact II when all the impulses have been sent. The relay P closes the circuit of the motor magnet D2, which rotates the selector VLW to find another idle junction. Supervisory signals and release. When the called subscriber replies, the relays A, B, Fig. 2, complete the circuit of a relay U, which reverses the connexions of battery and ground to the trunk a, b, thereby energizing a relay R2, Fig. 1, which disconnects the called subscriber's clearing lamp SL<11>. At the end of the call, the relays A, B, U all de-energize, and the lamp SL<11> again lights up. The clearing lamp SL<1> of the calling subscriber is controlled by the relay R1. The pre-selector VW returns to normal when the calling subscriber hangs up. The withdrawal of the plug 19 opens the circuit of the relay C, which restores the junction to its normal condition.