Patent GB-914622-A (GB)
Title: Improvements in and relating to arrangements for calling frequently wanted subscribers to automatic telephone systems
IPC: H04M1/274
Filed: 1960-11-17
Abstract: 914,622. Impulse transmitters. KANDA TSUSHIN KOGYO KABUSHIKI KAISHA. Nov. 17, 1959 [Jan. 14, 1959; April 17, 1959; Aug. 31, 1959], No. 38916/59. Class 40 (4). An impulse transmitter which generates pulse trains corresponding to the directory numbers of frequently wanted subscribers in response to actuation of a push-button particular to each wanted subscriber comprises a pile of metal discs, the peripheries of each of which are toothed according to a directory number and engage with a wiper contact. The pulses produced by the teeth are differentiated to provide trigger pulses to operate a multivibrator which generates pulses of equal length. As shown in Figs. 1 and 2, the discs are mounted on a shaft Sh with an angular position defined by the keyway Pr. The discs are in contact with each other by virtue of metal spacing sleeves Sl, a bolt being used to put the pile under pressure. Insulating discs Sd are placed between the discs and project to within a distance t of the crowns of the teeth. A set of wiper arms CS engage the disc peripheries except in the idle position where they overlie a notch Ur in common to the discs which allows them to be drawn off the shaft Sh without fouling the wipers. To each disc there is a push-button which when actuated connects up the associated wiper to an impulse regenerating circuit, starts a motor M to drive the shaft Sh at a constant speed, and activates a control circuit shown in Fig. 4. Also shown in Figs. 4 and 5 is a substation Te connected to the terminals L1, L2, of an exchange line which may also be connected to a loud-speaker SP. When a push-button SS connects up a wanted impulsing disc a switch SW1 coupled to the push-buttons operates momentarily, and thereby operates relay G which locks up and starts the motor M. The disc pile is rotated off normal by motor M and operates cams, not shown, to momentarily operate contacts EC1 and to hold contacts EC2 closed during the period of one drum revolution. Contacts EC1 initially operate relay S, which locks up, and then occupy a neutral position b until the end of the drum cycle. With S energized relay J operates and together they connect a loop across the line terminals L1, L2, including the contacts pl. Relay J also connects up loudspeaker SP which in consequence is energized by dial tone. Relay S also releases relay G. As shown in Fig. 5, which illustrates the device AD of Fig. 4, each connection made between a wiper CS and a tooth on a disc produces a pulse across resistor R6 the leading edge of which is differentiated and passed over Dd to trigger mono-stable multivibrator V1, V2, the output of which is amplified to operate relay P. The pulses are repeated by contact p<SP>1</SP> as break impulses to the exchange. Relay U operates to the first pulse repeated by P and holds up during the sending of digits to disconnect loudspeaker SP. At the end of a revolution contacts EC1 return to normal operating relay K and contacts EC2 break to stop the motor M. Relays U and S release. Loud-speaker SP is now connected over resistor R1 and will receive ringing tone. On reply the substation handset at Te may be lifted, thus operating relay H which disconnects battery to release all other relays. In the event of busy tone being received, a repeated recall switch SW3 may be operated to connect up the bi-metallic thermal delay switch TR1 which after a delay of about 15 seconds operates relay F over winding 2 and releases relays J and K to connect substation Te to the line. After a further 20 seconds the contacts of TR1 release, releasing relay F which while operated charges capacitor C1 and when released discharges Cl through relay G which locks up and initiates a further dialling cycle. The number of recalls is limited by a second bi-metallic thermal delay switch TR2 which, as energized over contacts of K and F, operates after five attempts at recall to release relays J and K while discharging capacitor C1 so that relay G can no longer be energized and switch TR1 is disconnected. Switch TR2 will also operate to disconnect the equipment should a directory number be dialled and the equipment be inadvertently left without switch SW3 set for recall. Receipt of an incoming call reverses polarity on the terminals L1, L2 so that any attempt to send a directory number from the drum of discs in this condition is frustrated by operation of relay F over winding 1 as soon as G operates to start the motor. With F operated J cannot operate and the drum cycles without the contact p1 being connected to line.