Patent GB-654155-A (GB)
Title: Improvements in or relating to communication installations
IPC: H04M1/31
Filed: 1947-07-28
Abstract: 654,155. Automatic exchange systems; impulse transmitters. MOSER, O. July 28, 1947, No. 20359. Convention date, July 26, 1946. [Class 40 (iv)] An impulsing mechanism at a subscriber's substation is driven by a step-bystep motor which is energized from an exchange power supply when an earth impulse is transmitted from the substation, separate lines and a common earth return being used for the drive and the impulsing circuits. Two embodiments are described, relating to the generation of a number of impulses depending on the value of a coin inserted in a coin freed mechanism and to the generation of dialling impulses selected by a key sender. Coin freed mechanisms, Figs. 1 and 2. A circuit is completed over switch hook contact HU1 and line wire b earthed over switch hook contact HU2 to start the preselector stage (not shown) at the exchange. Relay V operates from exchange battery on wire a, disconnecting the earth on line b at contact vl and releasing the coin inlet (not shown). Contact vl locks mechanically with the operated switch hook contacts. Insertion of a coin 1 displaces a lever 3 which closes an earthing contact an thereby short-circuiting the windings II of differential relays X and L which operate. Contact xl connects battery over wire b to the windings M<SP>1</SP>, M<SP>2</SP> of a stepby-step motor controlled by alternating contacts m1, m2. Contacts mk<SP>1</SP> to mk<SP>4</SP> are controlled by contact discs (not shown) as soon as the motor starts. Cams 4 and a toothed wheel 6 controlling impulsing contacts mi are rotated by the motor. The impulses generated by contacts mi are suppressed by shunt contacts mik until this contact is opened by lever 3, entering a depression in the cam. A cam is provided for each coin slot, the length of the depression and hence the number of effective impulses being arranged according to the monetary value of the adjacent coin slot. On completing one revolution a prominence on the cam displaces the lever and contacts an and mik are released. Contacts mkl to mk<SP>3</SP> are returned to normal by the contact discs and the motor is stopped by simultaneous excitation of both its windings M<SP>1</SP>, M<SP>2</SP>. Contact mk4 is mechanically locked to the released relay V and does not release until this relay re-operates to prepare the coin conduits for the insertion of a further coin. Opening of contact mk<SP>4</SP> de-energizes both windings of the differential relays X and L and battery is disconnected from wire b by the release of contact xl. On completion of coin insertion, dialling is carried out over impulsing contact i with contact k operated. A coin insertion indicator is operated by a stepping relay NA which is only energized by the coin insertion impulses since shorting contact mk<SP>3</SP> is otherwise closed. On commencing dialling the operation of contact k connects relay A in circuit. Contacts al and a2 close and lock mechanically to the hook switch, preventing further operation of relays A and NA until after the receiver is replaced. Supplementary payments in the event of polongation of the speech period are therefore not indicated. The operation of a relay KM by a positive potential applied between wire a and earth effects the coin collection after the telephone connection is established. Coin return is effected by a return magnet RM operated by a similar potential applied to wire b. Impulse transmitters, Figs. 3, 5 and 7. The subscriber's loop circuit is completed over switch hook contact HU1. Depression of a key 14 in the key sender closes contacts an<SP>1</SP> and opens contacts t11 and t21 in sequence. Contact an<SP>1</SP> short circuits windings II of differential relays X and L at the exchange and also the telephone receiver. A step-by-step motor is started over its winding m<SP>11</SP>, m21 in an identical manner to that in the previous embodiment. A gear-wheel 19 depressed by the key couples a control disc 13 to the motor shaft 12. The key is held in a depressed position by a spring 20 engaging a shoulder 21 and is released when a pin 22 on the rotating control disc strikes a lever 23. Impulses generated by a toothed wheel 15 (not shown) and contact i1 are transmitted while contact t21 is opened. Release of the key stops the motor over closed contacts t11, the line being re-established to its initial condition when contact an<SP>1</SP> is released. The control disc is returned to its normal position against a stop 26 by a spiral control spring 25. As shown, the same control disc is used for two numerals, the pins 22 controlling the number of effective impulses being located on opposite sides of the disc.