Patent GB-612925-A (GB)
Title: Improvements in or relating to call metering in telephone systems
IPC: H04Q3/00
Filed: 1946-06-06
Abstract: 612,925. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. June 6, 1946, No. 17263. Convention date, June 23, 1945. [Class 40 (iv)] The D.C. booster voltage for operating a service meter is obtained by rectifying and filtering part of the output of a source of alternating ringing current. A voltage discriminator comprising a gaseous discharge tube is connected in series with the meter to prevent its operation to voltages below the booster voltage. As shown, the metering is controlled from a repeater R on seizure of which relay 4 pulls up. Relay 5 follows, busies the trunk, and holds for the duration of the call. Battery reversal on the reply of the called party operates polarised relay 15 which is followed by 16. The common metering impulse equipment comprises two cam wheels 17, 18 driven at 30 r.p.m. by the motor M energized by the ringing current supply. Associated with wheel 17 are four make-before-break spring sets controlled by four springs 20-23 which are raised successively by the cam 24 during rotation of the wheel. The source of D.C. booster voltage 67 is fed from the A.C. ringing supply and the filtered rectified output is connected by lead 66 to the springs 20-23 in parallel. Ground from contact 25 is normally extended over two, three or four of the spring-sets to leads 28, 29, 30 respectively, which are multipled to contacts such as 41 of relays such as 8 associated with the repeaters. In the example illustrated, the contact 41 is connected to lead 30 so that four metering impulses will be received over lead 66 during one revolution of the cam wheel 17. Operation of relay 16 in the repeater brings up relay 8 and start relay 19. Relay 8 disconnects the private wire 12 from direct ground, connects it to the metering impulse lead 30, and locks-up over its lower winding. As soon as the cam wheels 17, 18 commence rotation shoulder 46 of wheel 18 closes contacts 43, 44 and opens contacts 40, 44, thus holding relay 19 and opening the operating circuits of the relays 8 of the other repeaters in the group during the entire metering period. After the wheel 17 has operated all four spring sets, member 42 on wheel 18 momentarily closes contacts 43, 44, 45 to bring up the release relay 36 which disconnects relay 8, after which the spring set 40, 43, 44, 45 restores to normal and if no relay 16 in the group is operated the motor M stops. Multiple metering. The metering cycle may be repeated at 3-minute intervals under control of cam wheel 53 driven by motor 54 which is started up when relay 36 is operated. After 3 minutes, cam 65 opens contacts 51, 52 and releases 36, the cam wheel resetting automatically to its initial position. Relay 8 re-operates and the metering cycle is repeated. Voltage discriminator. A gaseous discharge tube 76, e.g. a neon bulb, is connected in series with the meter 77 and the booster voltage is made higher than the striking voltage of the tube and below its drop-out voltage so that since all these voltages are well above the normal exchange battery voltage the meter is effectively disconnected from the private wire except when booster voltage impulses are applied to it.