Patent GB-181709-A (GB)
Title: Telephone exchange systems
IPC: H04B10/00
Filed: 1922-06-12
Abstract: 181,709. Snijders, G. C. June 14, 1921, [Convention date]. Automatic exchange systems.-Connections are established by selectively associating sources of light with selenium or other light-sensitive cells, the controlling impulses, test-currents and speech-currents being repeated by photophone action. The' drawings represent an exchange of 10000 lines, the individual apparatus of calling and called subscribers being shown in Figs. 1 and 4, while Figs. 2 and 3 show a trunk comprising a line finder and connector. For outgoing calls each subscriber's line is equipped with lamps 15, 17 and a light-sensitive cell 16, mounted on a single A-board, for co-operation with call-finder cells 59, 45 and lamp 54. For incoming calls each line is equipped with lamps 18, 20 and a cell 19, mounted on a single B-board, for co-operation with connector cells 135, 125 and lamp 132. The lamps and cells are provided with directive tubes. The call-finders are of simple rotary construction but the connectors are of the co-ordinate type, having a rotary movement controlled by the thousands and hundreds digits and a vertical movement controlled by the tens and units digits. Specifications 178,917, [Class 40 (v), Wireless signalling &c.], and 176,796, [Class 40 (ii), Phonographs &c.], are referred to. Construction of connectors. In the second position of a sequence switch 200, Fig. 2, the thousands impulses control a relay 70, which reverses the battery connections of a magnet 75, so that a rotor 76 having four poles of alternate polarity gives a quarter turn to a shaft 79 at the commencement and again at the end of each impulse. This rotation is communicated through gearing 82, 84, 85 to a contact 89, which is moved ten steps for (each impulse. At the termination of the digit the sequence switch 200 moves to its 3rd position and energizes a changegear magnet 83, so that the hundreds impulses rotate the contact 89 one step for each impulse, through gearing 82, 84, 86, 87, 85. The switch 200 then moves to its 4th position and energizes a solenoid 94, which rotates the connector until a contact 91 engages the contact 89, whereupon the relay 92 de-energizes the solenoid 94 and energizes a clamp magnet 98. In a similar manner, in the 4th and 5th positions of the switch 200, the tens and units impulses operate a rotor 101 to position a contact 114, and in the 6th position of the switch 200 a solenoid 119 raises the connector until a contact 116 engages the contact 114, whereupon the relay 117 deenergizes the solenoid 119 and energizes a clamp magnet 123. The lamp 132 and cells 135, 125 partake in the rotary and vertical movements of the connector. When the switch 200 leaves its 12th position the clamp magnets 98, 123 are de-energized to allow springs 97, 122 to restore the connector, and magnets 146, 148 are energized to disengage the contacts 89, 114 from the pinions 85, 110, allowing the contacts to return to normal position. Call finder. The line relav 10 of a calling line lights the line lamp 17 and busy lamp 20. When the cell 45 of a rotary finder comes under the influence of the lamp 17 it energizes a relay 46, which open-circuits the power magnet 41, energizes the brake magnet 44, drives the sequence switch 200 to its 2nd position, and energizes a relay 49 and magnet 59. The magnet 57 operates a shutter to expose the cell 59. The relay 49 lights the lamp 54, which excites the cell 16 to energize relay 21, which extinguishes the line lamp 17 and lights the speaking lamp 15. The lamp 15 excites the cell 59 to energize relay 62, which energizes relays 66, 68. Connector. The impulses dialled by the subscriber are repeated by relay 10 through the lamp 15 and cell 59 to relay 62, which repeats them to relay 70, which controls the connector as previously described. The last impulse of each series is prolonged sufficiently to de-energize the sluggish relay 68, which moves the switch 200 to its next position, but relay 66 is still more sluggish and holds up. When the setting of the connector has been completed, a circuit 216, 118, 140, 210 is closed by relay 117 to drive the switch 200 to its 8th position. Busy test. If the wanted line is busy its lamp 20 is lit and excites the cell 125 to energize relay 126, and busy tone current is transmitted through contacts 218, 219. Supply of ringing current. If, however, the wanted line is idle, so that relay 126 is not energized, a circuit is closed over contact 127 to energize relay 142, Fig. 2, which drives the switch 200 to its 9th position. Magnets 128, 130 are energized in series with relay 142 and operate shutters to expose the lamp 132 and cell 135 and to cover the cell 125. The lamp 132, which is energized at contact 204, excites the bell 19 to energize relay 24 which energizes relay 30 to supply ringing current. The ringing current flickers the speaking lamp 18 to send back an audible tell-tale signal to the calling subscriber. When the called subscriber answers, his line relay 10 deenergizes the ringing relav 30 and lights the busy lamp 20 and lamp 18. The lamp 18 excites the cell 135 to energize relay 138 which drives the switch 200 to its 10th position. Conversation. The calling subscriber's voice is transmitted through transformer 9, lamp 15, cell 59, amplifiers 144, transformer 134, lamp 132, cell 19, and transformer 9, and the called subscriber's voice is transmitted over a similar channel through the lamps 18, 54. Release. When the calling subscriber disconnects himself the extinction of lamp 15 leads to the de-energization of the sluggish relay 66, which drives the switch 200 to its 16th position, and the connector is restored as previously described. When the called subscriber disconnects himself relay 138 is de-energized and closes a circuit 150, 151, 140, 210 to drive the switch 200 to its 18th position, whence it is driven to normal over a circuit 67, 207. If the calling subscriber fails to disconnect himself the called subscriber moves his switch-hook up and down several times to energize and de-energize the relay 138, which closes circuits for driving the switch 200 to its 18th position, whereby the connector is released. A lamp 153 is lit until the calling subscriber also disconnects himself. Preventing simultaneous connections to same line. If two finders reach a calling line simultaneously the cell 16 is doubly illuminated and energizes a marginal relay 39 which opens the circuit of lamp 15. The relay 62 in each finder is therefore not energized and the switch 200 continues moving until it returns to normal. Similarly if two connections are made simultaneously to a wanted line a marginal relay 40, Fig. 4, is energized, which prevents energization of the ringing relay 30 and connects alternating current to the lamp 18 to give both calling subscribers an audible signal. Connection to a private branch exchange having several lines. The busy lamps 20 of all the P.B.X. line; except the last have a greater brilliancy than those of single lines. Consequently if the first line is busy a marginal relay 139, Fig. 3, is energized and sends an impulse to relay 70 to give the connector an extra vertical step, and this action continues until an idle line or the last line of the series is reached. Inter-exchange working. One or more vertical columns of the connector may be allotted to calls to other exchanges.