Patent GB-254183-A (GB)
Title: Improvements in automatic and semi-automatic telephone systems
IPC: H04Q3/42
Filed: 1925-12-05
Abstract: 254,183. Standard Telephones & Cables, Ltd., and Lowry, L. P. Dec. 5, 1925. Semi-automatic exchange, systems.-In a semiautomatic system in which an idle sending- mechanism is temporarily associated with an operator's keyboard and in which means are provided for cancelling a partly set-up call, the sending-mechnism is held busy during the cancelling operations so that the same mechanism will be used if a second attempt to set up the call is made. The timing means which causes the call to be routed to a special operator and the sending-mechanism to be released if a complete call is not set up within a given time is reconditioned when a partial setting is cancelled so that the, onerator is allowed the full time interval for effecting the second setting. The invention is described with reference to a system in which a semi-automatic B-operator assigns an idle trunk circuit, Fig. 3. and on the depression of the assignment key AS, a finder-switch TFS hunts for the assigned trunk whilst a hunting switch SFS hunts for an idle sending-mechanism, Figs. 4 and 5. Both these switches form part of an outlet relay group, Fig. 2, which is already temporarily associated with the operator's keyboard, Fig. 1, by means of a preselecting switch OFS. A further feature of the invention relates to the provision of a common starting relay for both hunting switches TFS, SFS. The system described also contains the following features which form respectively the subject-matter of Specifications 253,574, 253,575, and 255,130 :-(1) The operator's equipment, Fig. 1, is provided with duplicate sets of apparatus, the change-over from one set to the other being effected either manually by the operation of a key or automatically on the development of a fault in the set in use. (2) The finder switch TFS, Fig. 3, is provided with a test wiper of the bridging type to ensure that the switching relay will not operate prematurely owing to the temporary removal of short-circuiting earth when the switch moves from one set of contacts to the next. In order that when the switch moves on to the marked terminals the temporarily-bridged earth may not prematurely operate the relay K which should not operate until earth is set back from the outlet relay group, Fig. 2, this relay is made slow-acting. (3) The impulse-sending mechanism, Figs. 4 and 5, is marked continuously busy during the release until all the component parts are fully restored to normal. The mechanism has motordriven interrupter springs which are tested as to their operative condition each time the apparatus is taken into use and if they are fautly, i.e. either permanently open or permanently closed, an alarm is operated and the sending-mechanism is marked busy. The various Figures of the drawing should be arranged with Figs. 1, 2, 4 and 5 in order from left to right and with Fig. 3 above Fig. 2. Connection of outlet relay group, Fig. 2. to assigned trunk and to idle sending-mechanism. The depression of the assignment key AS, Fig. 3, energizes relay H which removes earth from the test terminal P, and completes a circuit for relay HC, Fig. 2. This latter relay acts as a common starting relay for the switches TFS, SFS for which it closes stepping circuits TFM, HC7, TG8, P and SFM, HC9, FC10, wiper 1,. respectively. When the assigned trunk is found, switching relay TG operates in series with magnet TFM and when an idle sending- mechanism is found switching relay SG operates in series with magnet SFM. When both switches have completed their operations relays K, SW operate, the former over the circuit CBK, H6, TG8. SG14, SG8 and connect the'operator's keyboard DR, Fig. 1. through to the sending- mechanism. Relay SG extends earth over wiper 1 of switch SFS to operate relay G. Fig. 4, which closes a point in the busy chain circuit BE, SB, and prepares a circuit for the common supervisory lamp SL so that the operation of the common key SK at any time will indicat.e which of the sending-mechanisms are busy. When the distant A-operator plugs into the assigned trunk, relays B, C operate, the latter closing the motor circuit for the flicker interrupter FR and opening the flash circuit from interrupter FH, Fig. 1, so that if the A-operator plugs in before relay K operates, the lamp TL will flicker, whilst if relay K operates before the A-operator plugs in the lamp will flash. When relay K has operated and the A-operator has plugged in, relay J operates, causing lamp TL to glow steadily. Registration of wanted number. The four digits of the wanted number are then successively set up on the keyboard DK and are in various combinations over wipers 3 - - 6 of switches OFS, SFS and wipers 62 - - 140 of the input control switch ICS to the register sets MA - - MD &c. The operating circuits of the register relays pass through relay Q which controls the stepping of the switch ICS. In the 2nd position of this switch, wiper 36 completes a circuit over contacts M28, H14 for relay R which remains operated and in the 5th position is locked up over wipers 62, 36 and contacts M6, P28. When the switch ICS reaches its fifth position, earth is sent back over lead 3 to operate relay P, Fig. 1, which in turn energizes relav PC, Fig. 2. Relay PC releases relay SW and completes circuits for magnet OFM which causes the switch OFS to connect the keyboard to the next idle outlet and for relay PS which extends earth over the circuit J29, OC, PS5, and wiper 2 of switch SFS to indicate that sending may commence. Transmission of impulses. Relay M. Fig. 4, in operating, completes the motor circuit MS for driving the interrupter springs, connects up springs SIS, connects up the interrupter-earth lead EI to flash the supervisory lamp SL, and unlocks relay R which releases slowly. At the next closure of springs SIS relay H operates over its lower winding to close contacts 6 and at the succeeding interruption relay H operates fully over front contacts of relay R and locks over contacts H16, F8, M34. Relay H connects springs SIS to the magnet RSS of the sending switch SSS and also connects up impulsing springs ITS so that at the next closure of the latter, relay N operates partially and at the succeeding opening operates fully and places springs IIS across the outgoing impulsing leads. As soon as switch SSS moves from normal, relay E removes a short circuit from springs IIS and impulsing then proceeds until the upper wiper of switch SSS finds the terminal earthed by the register set MA - - MD, when relay F operates to prevent further impulses, releases relay H and closes a restoring circuit for switch SSS. Relay R then operates again, relay H is operated by. springs SIS as before and the transmission of the remaining digits proceeds in a similar manner, the stepping of the output control switch OCS being effected by relay F. When the latter switch reaches its 5th position at the conclusion of impulsing, its wiper 36 completes a circuit for relay P, Fig. 4, which (1) connects earth to incoming lead 6 to energize relay FC, Fig. 2, which effects the release of relays PC PS, TG, H, K, (2) bridges leads 4, 5 to prevent the transmission of any further accidental impulse, (3) maintains relay R operated, (4) places guarding earth on the test lead 1, (5) operates a meter TM, and (6) releases relay M. The relapse of relay G now completes restoring circuits for switches ICS, OCS and when both have returned to normal, relays P, N, R release, lead 1 being earthed until release is complete over contacts P15, G28, R11. When the called subscriber replies, relay D, Fig. 3, operates and connects up the coil A to give a supervisory signal to the A-operator. Faulty sending-apparatus. If springs SIS are either permanently open or permanently closed, relay H does not operate and upon the release of relay R relay P operates over contacts G34, N8, R6, H8, M32 and connects up the common urgent alarm UA in series with the individual supervisory lamp SL. Relay P locks over the release key RK and maintains the sending- mechanism busy until forcibly released. If springs IIS are similarly faulty, relay N does not operate and when relay H releases, relay P operates as before. Faulty outlet, Fig 2. If a fuse blows, relay FB operates over lead FAB. marks the outlet busy to switch OFS and lights the busy lamp OGL. The throwing of key CB produces a similiar effect. Faulty outlet finder; provision of duplicate apparatus. The apparatus, Fig. 1, associated with the keyboard DK comprises relays O, P. Q. R and an outlet-finder switch 1 - - 6 whilst a duplicate set of apparatus comprises relays EO - - ER and a second switch E1 - E6. The change over from one set to the other is effected by relays E, EB which operate in series over either of their windings. With the circuits as shown, the first set is connected up and relays EA, EB are not operated since lead G is normally disconnected from earth. Lead F is however normally earthed so that operation of key EK brings the second set into use. This set is also brought into use by the blowing of a fuse associated with the first set which effects an earthing of the lead G. Similarly the blowing of a fuse associated with the second set removes the normal earth connection from lead F so that relays EA, EB release and bring the first set again into use. All sending-mechanisms busy. If all the sending-mechanisms available to the switch SFS are busy, relay FB energizes over the chain circuit BE, SB, marks the outlet busy and lights the busy lamp OGL. Cancelling faulty setting. A partly set-up call may be cancelled before impulse transmission starts by depressing key CK, Fig. 2, which energizes relay FC to remove earth from wiper 1 of switch SFS. Relay G in the sending-mechanism releases, restores any operated registers and the switch ICS and marks the mechanism busy until restoration is complete. Relay FC closes a circuit for relay CG which operates to earth wiper 1 and marks the sending-mechanism busy