Patent GB-269233-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1926-01-06
Abstract: 269,233. Automatic Telephone Manufacturing Co., Ltd., and Taylor, R. Jan. 6, 1926. Automatic exchange systems. - A telephone system in which a talking connection over automatic switches is controlled by the calling subscriber from the connector, is provided with apparatus for automatically releasing the connector independently of the calling subscriber at a timed interval after the called subscriber has hung up. The said apparatus is common to a number of battery-feeding switches. The apparatus also comprises common equipment for routine tests on the said switches. Release of connection independent of the calling subscriber. The battery-feeding switch (in this example, the connector) is of well-known type. When the called subscriber hangs up, the back-bridge relay D de-energizes, while the ring- ing cut-off relay F remains energized. A relay is energized in series with a lamp LP, which completes a circuit for the stepping magnet D' of a Hunting switch 1 - - 6. When the wipers of the hunting switch reach the required contacts, a relay CO energizes over the wiper 2 and the test-wire 9 to break the circuit of the magnet D<1> at 22 and to stop the switch, to short-circuit the relay L and directly energize the lamp LP. to complete a circuit for the clock contacts CC and a timing relay 27, and to prepare a locking circuit at 26 for the two-step timing relays 27 - - 32. If the connector is connected to the normal contacts of the wipers, the relay CO energizes at once and prevents the switch hunting. The contacts CC close every half-minute; on closing, the relay 27 energizes to pull up its light armature 34, and on opening, the relay locks over its whole winding to pull up the armature 33 which prepares a circuit for the relay 28. The last relay 32 locks up three minutes after the called subscriber hangs up, and at the same time completes an alarm circuit at 37, completes a circuit for the lower winding of relay CO over contacts 35, a wiper 4 and test wire 9, and at 36 completes a circuit for the release magnet Z over the wiper 3 and the off normal contacts of the switch, so that the latter releases. The attendant, warned by the alarm, locates the switch by the lamp LP and breaks down the connection. Relay CO then de-energizes and a circuit is formed for the magnet D<1> over the homing wiper 1 to return the hunting switch to normal. If the calling subscriber hangs up during the three minutes, relay CO will de-energize and and locked timing relays will at once release, so that there is no danger of cumulative action. The whole connection might be released, if, for instance, the earth extended over the wiper 3 energized a slow-release relay to cut out the line relay A. Routine tests. A test plug inserted in a jack J energizes a relay S which connects up the magnet D<1> over the plug-and-jack and the wiper 4 to the test-wire of the connected switch to step the hunting switch, if necessary, to an idle connector. The relay S also cut out the relays L. CO. The key K is thrown, and a circuit including the dial springs DS, the wipers 5. 6 and the line relay A is formed. The attendant manipulates his dial to test the connector, and then restores the key to release the connector. Before the relay B releases, the magnet D<1> is energized over the wiper 4 to hunt for the next free connector. If the hunting switch is not at normal when the plug is withdrawn, release of the relay S completes a homing circuit therefor.