Patent GB-191326602-A (GB)
Title: An Improved Method of and Means for use in Connecting an Automatic Telephone Sub-station System to an Automatic Central Station.
Inventor: STEIDLE HANS CARL
Filed: 1913-11-19
Granted: 1914-05-14
Abstract: 26,602. SteidlÚ, H. C. Nov. 19. Automatic exchange systems.-In a system in which a line L from an automatic exchange is provided with automatic extension apparatus NU for several substations, the extension switchboard battery SB is fed from the exchange battery LB in the intervals when the line L is not in use. The feeding-current passes over both sides of the line in parallel, the relays R3, P, RR, E and the resistances w3, w4 being included in its circuit. The current is sufficient to energize the relays RR and P but not the relays E and R3. The circuit arrangements are such that if the exchange or extension switching-apparatus is set in an off-normal position by a momentary earthing of the main or extension lines, or by mechanical interference, the apparatus automatically restores itself to normal. Calls from extension substations to main exchange. The subscriber N2 presses a key AT which energizes the left-hand winding of his individual relay R2 at the extension switchboard. The relay R2 closes a locking-circuit through its right-hand winding in series with the meter Z2 and relay W, and the relays R2, W jointly effect the connexion of the exchange line L to the extension line N2. The resistances w3, RR, &c. and the counter-electromotive force of the battery SB are then removed from the main line L, so that the current is increased sufficiently to energize the exchange relay R3, which starts the preliminary selector VW hunting for an idle group selector in known fashion. The de-energizition of the relay RR prevents the energization of the individual relay of any other extension subscriber who may call while the line L is engaged. At the same time a relay A energizes the magnet EM of the extension selector SR, which moves a step from its normal position and energizes a slow-release relay V. During the operation of the impulsesender WS, which grounds the line b while intermittently interrupting the line a, the relay A remains energized, being of slow-release type. When the subscribers hang up their receivers, the exchange selectors are released and the relay A deenergizes, completing a circuit for the release relay RR over the line b. The relay RR energizes the magnet RM, which (1) restores the selector SR, and (2) unlocks the circuit through the relays R2, W and the meter Z2, Finally, upon the de-energization of the slow-release relay V, which was opencircuited by the restoration of the selector SR, the magnet RM is de-energized. Calls from the main exchange to extension substations. The connector LW, by applying full battery-potential directly to the line b, increases the current sufficiently to energize the relay E. The relay E energizes a slow-release relay U, which cuts out the relay RR so as to prevent the energization of the individual relay of any extension subscriber who should call while the line L is engaged. The battery connexion to the lead b is now interrupted a number of times to de-energize the relay E, which energizes the magnet EM to set the selector SR in a position corresponding to the wanted line. Finally, the battery connexion to the lead b remains open, de-energizing the slowrelease relay U, and the connexion is completed by the energization of the relay W in series with the individual relay R2 of the wanted subscriber. Ringing-current is supplied from the connector over the a side of the line. At the end of the conver ation, the release of the apparatus takes place as already described.