Patent GB-191311177-A (GB)
Title: Telephone Exchange System.
Inventor: CORWIN ELMER REED
Filed: 1913-05-13
Granted: 1914-05-13
Abstract: 11,177. Corwin, E. R. May 13. Semi - automatic exchange systems. - The selection of the wanted subscriber is controlled by the application of test-potential to the terminals of forwardly hunting switches by means of the operator's keyboard. In the system described, a calling line 1, Fig. 4, is connected by a call-finder 52 over leads 64 to an operator 65, who enquires the connexion desired and then writes it down on her keyboard, which comprises sets of keys for the hundreds, tens, and units digits, three of each set being shown in Fig. 5. The operator then depresses a starting-key, whereby a second callfinder 72, permanently associated with a forwardhunting non-numerical switch 80, functioning as a first selector, is set in operation and makes a connexion with the calling line independent of that through the first call-finder 52. The connexion is extended through similar selectors 80, 32, 37, to the called line 2, under the control of the operator's keyboard, which is released when connexion is made with an idle subscriber, the release being under the control of the subscribers. Construction of selector. When the holding-magnet L, Fig. 6, is energized, an extension c of its armature moves the pawl d of the motor magnet M into the position shown in dotted lines, in which it engages a spring catch a. As the selector reaches its normal position, a finger f on the ratchet trips the catch a and releases the pawl d. Connexion of calling line to idle operator. When a calling subscriber 1 removes his receiver, his line relay 45 energizes in series with a relay 47, common to a group of lines. The relay 47 connects the battery 48 through an interrupter 49 to the motor magnet 51 of the lower call-finder, or, if this is engaged, over the front contact of its relay 50 to the motor magnet 51 of the upper callfinder. The wipers 53 ... 57 are rotated until the test wiper 57 engages the test contact 62 of the calling line, when a circuit is closed from the battery 48 through the upper winding of a relay 15, lowest armature of relay 45, contacts 62, 57, relay 50, and the armature of relay 63, Fig. 5, to ground. The relay 50 disconnects the motor magnet 51, and locks up over a circuit including the upper winding of relay 15, which has previously attracted its armature, contacts 59, 54, relay 50, and the armature of relay 63. The holding-circuit for the upper winding of relay 15 also includes both sides of the calling line and the line relav 45. The relay 15 removes the batterv connexion from the test terminal 62 so as to prevent other call-finders seizing the calling line. The calling line is connected through the wipers 53, 54 to the operator 65, who enquires the connexion wanted. Construction and operation of operator's keyboard. The keys are retained in their depressed positions by the engagement of spring-pressed levers 82, Fig. 5, in notches 86, and are released by the armature of the magnet 81. The battery 11 is connected through series contacts of the keys to the magnets 81 of each set of keys. The depression of a hundreds key connects the batterv 11 to one of the set of wires a over a contact 83, and the depression of tens and units keys similarly connects the battery 11 to one of the sets of wires b, c, but in these cases the connexion is only complete when the preceding hundreds or tens key is released. Connexion of calling line to first selector. The operator writes down the connexion required upon her keyboard and then depresses her starting-key 66, which (1) establishes a fresh ground for the relay 50, Fig. 4, independent of the relay 63, and (2) by closing contact 70 closes a circuit for the motor magnet 620 of a call-finder 72, which extends from the battery 48 through the interrupter 49, motor magnet 620 of the lower call-finder, normal contact of relay 71, front contact of relay 15, wiper 56, and contact 70 to ground. If the lower callfinder is in use, the circuit extends through the motor magnet 620 of the upper call-finder 72, and the front contact of the relay 71 of the lower call-finder. The magnet 620 rotates the wipers 73, 74, 75 until the test wiper 75 engages the contact 78 of the calling line, when the relay 71 is energized over an off-normal contact 79, relay 71, wipers 75, 55, and relay 63 to ground. The relay 71 disconnects the motor magnet 620, and locks up over wiper 74, both sides of the calling line and line relay 45. The relay 63 locks up over contact 69, thus removing the ground connexion on the contact 78 of the calling line, which is now connected by the wipers 73, 74 to the wipers 27 of the first selector. First selector. The circuit of the motor magnet 79 is now completed from the battery 48, interrupter 49, magnet 79, normal contact of relay 31, wiper 73, and line relav 45 to ground. The wipers 27, 30 are rotated step by step until the wiper 30 engages the contact to which potential has been applied by the depression of a hundreds key, when a circuit is closed from the battery 11, magnet 81 of hundreds key, contact 83 of depressed key, wire a, normal contact 29 of a second selector, wiper 30, upper winding of a relay 31, off-normal contact 84, wipers 75, 55, and front contact of relay 63 back to the battery 11. The magnet 81 releases the depressed hundreds key, and the relay 31 disconnects the magnet 79 and locks up over its lower winding. The calling line is now extended to the wipers 24 of a second selector. Second selector. The motor magnet 87 is energized by current from the battery 48, interrupter 49, magnet 87, normal contact of relay 36, wipers 27, 73, and line relay 45 to ground, and rotates the wipers 24, 35 until the wiper 35 engages a terminal connected to the battery 11 by the depressed tens key, when the tens key is released, and the relav 36 energized as in the case of the first selector. Final selector. The calling line is thus connected to the wipers 21, Fig. 4, of the final selector, the motor magnet 100 of which is energized over the normal contact of relay 39, and wipers 24, 27, 73, and relay 45. The wipers are rotated until the wiper 38 engages the contact corresponding to the depressed units key, when if the wanted line is disengaged, a circuit is closed from the battery 11, through the release magnets 81 and series contacts of the hundreds, and tens keys, magnet 68, release magnet 81 of the units keys, one of the leads c, the lower winding of relay 16 of the called line, wiper 38, the upper winding of relay 39, off-normal contact 34, wipers 35, 30, off-normal contact 84, wipers 75, 55, back to the other pole of the battery 11. The relays 16, 39, and magnets 68, 81 are thus energized. The relay 39 disconnects the motor magnet 100, and locks up over its lower winding. The magnet 81 releases the units keys, and the magnet 68 releases the depressed starting-key 66, thereby removing the ground connexion for the locking-magnet 50, which then releases the connexion between the calling line and the operator. If the wanted line is engaged, its relay 16 is energized, so that the circuit of the relay 39 and magnets 68, 81 is not completed. The final selector continues to rotate until either the wanted line becomes free, or the calling subscriber hangs up. The non-release of the units key of her keyboard indicates to the operator that the desired line is busy, and she informs the calling subscriber. Supply of ringing-current. The relay 16 of the called subscriber, energized as described above, locks up over a circuit from the battery 48, upper winding of relay 16, the lower of the two wipers 21, 24, 27, wiper 74, both sides of the calling line and relay 45 to ground. The relay 16 closes a circuit through the interrupter 88 and ringing-relay 46, which connects the generator 89 to the called line. During the first non-ringing interval after the called subscriber answers, his line relay 45 disconnects the ringing relay 46 and connects both sides of the line to the contacts engaged by the wipers 21. Release. When the subscribers replace their receivers, the relays 15, 16, 31, 36, 39, 71 are all de-energized, and return the selectors &c. to normal.