Patent GB-738372-A (GB)
Title: Improvements in or relating to metering in automatic telephone exchanges
Inventor: FLOWERS THOMAS HAROLD
IPC: H04Q3/00
Filed: 1950-06-07
Abstract: 738,372. Automatic exchange systems. POSTMASTER GENERAL. Sept. 20, 1951 [June 7, 1950], No. 14242/50. Class 40 (4). Variable fee metering equipments each associated with a trunk or junction are connected in multiple over metering marking leads to the marker for setting up the connections and when the associated trunk or junction is seized for a connection the metering equipment controls the emission of metering pulses in accordance with the markings applied by the marker to the metering marking leads. In setting up a connection over first and second rank switches 10, 20, Fig. 2, respectively, the marker M marks a junction lead ML1 ... ML4, a trunk lead GM1 ... GM3 and none, one or more of metering marking leads MM1 ... MM4 commoned to all the metering equipments in that part of the exchange served by the marker M. Metering equipment MJ3, MJ4 is provided only for junctions J3, J4 dealing with calls to be metered according to one tariff system and which are mainly subscriber originated. Otherwise the metering equipment is associated with the trunks between the switch ranks, the choice of trunks determining the tariff system to be used. Trunks T1, T2 not provided with metering equipment are used for transit calls and calls to junctions J3, J4. In a metering arrangement suitable for use in the system described in Specification 722,174, the code digits bring about the operation in the marker, Fig. 3, of one of relays 31 ... 35, there being one relay for each fee value for each route. The operated relay applies a 50 v. marking to a metering lead or leads MM1 ... MM4, extinguishes a tube V1 or V2 to mark the junction leads ML1, ML2 or ML3, ML4 and fires one of tubes V3 ... V5 to mark a trunk lead GM1 ... GM3. When the junction or trunk 11, 12 with which the metering equipment for the connection is associated is seized, a normally conducting tube V41 is extinguished, whereupon a tube V42 oscillates at 1000#. The oscillator output is rectified and smoothed and raises the potential of a lead 21 to 150 v. at which it is held by the clamping rectifier MR44 to prime a tube V43. Metering according to connection obtained. The potential rise of the lead 21 fires a tube V51 in the metering equipment, Fig. 5, whereupon a positive pulse is applied to the grids of register tubes V52 ... V55 so that the tube, say V52, primed by the marking applied to leads MM1 ... MM4 conducts. The answer pulse actuates a voice frequency receiver VFR and after a delay due to a condenser C42, V43 fires and V60 follows to open a rectifier gate MR51. The first pulse P1 fires a tube V56 primed by the register tube V52 which is extinguished. With V56 conducting, a lead 41 becomes positive and actuates a static switch which couples a V.F. generator G41 to the line 12 to send a metering pulse to the calling subscriber's line equipment which may be similar to that described in Specification 722,174. The next pulse P1 fires V53, whereupon V56 extinguishes and terminates the metering pulse. In response to the pulses P1, V57, V54, V58, V55, V59, V61 conduct in turn, each pulse starting or ending a metering pulse. Thus the number of metering pulses is determined by the first register tube to conduct. Tube V61 fires V62 to extinguish V60 which closes the gate MR51. When the clearing signal is received, V41 conducts and cuts off the oscillator V42 and the circuits are returned to their normal condition. Metering according to connection obtained and duration of call. The rate at which metering pulses are to be sent is determined by the markings on leads MM1 ... MM4, Fig. 7. When lead 21 is raised to 150 v., V73 conducts and feeds a pulse to the control grids of the register tubes V74 ... V77 sufficient to fire the tubes primed by the markings on leads MM1 to MM4. In response to the answer signal a pulse derived from the lead 31 operates V71, providing a register tube is conducting, followed by V78. The latter is extinguished after a delay caused by a condenser C80 and equal to the length of a metering pulse by the firing of a tube V79. When the tube V78 conducts lead 41 becomes positive so that a metering pulse is reverted. With V71 conducting, a combination of pulses P2 ... P5, Fig. 8, determined by the fired register tubes is applied through rectifier gates MR79 ... MR82 to a lead 61. The first pulse on the lead 61 after V79 conducts fires V80 and the second V81. Thereafter V81, V82, V83 conduct cyclically. Each time that V83 strikes, a pulse is applied to the grid of a tube V70 which primes V72 and brings the lead 41 to a positive potential so causing a metering pulse to be sent. After a period determined by the staggering of the pulses P1 with respect to the pulses P2 ... P5, a pulse P1 fires V72 which extinguishes V70 to end the metering pulse. This arrangement which results in each third pulse on the lead 61 producing a metering pulse reduces the inequalities in spacing of the metering pulses as compared with those which would result if the time intervals between pulses P2 ... P5 were three times as great and each pulse were effective to produce a metering pulse. The inequality of spacing may be further decreased by increasing the rate of the pulses P2 ... P5 and the number of the tubes V79 ... V83. The metering equipment returns to normal when the potential of lead 21 falls as a result of the clearing signal. Specifications 694,092 and 722,172 also are referred to.