Patent GB-701590-A (GB)
Title: Electric calculating apparatus
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H04M3/36
Filed: 1950-12-21
Abstract: 701,590. Automatic exchange systems. SIEMENS BROS. & CO., Ltd. Nov. 30, 1951 [Dec. 21, 1950], No. 31170/50. Class 40 (4) [Also in Groups XXXVI and XXXVIII] Electric apparatus provides a continuous estimation of the average elapsed waiting period of the existing members of a queue. As shown the apparatus is used in conjunction with call distributing arrangements such as described in Specification 634,828, in which each incoming call seizes a distributer having outlets to queue circuits and to connecting circuits at operators' positions. If the queue is empty and no connecting circuit is assigned the first distributor taken into use stops at the first queue outlet (the last queue outlet in the bank), whereupon the first queue relay A operates. Relays EN, H, HA, X, Y operate in turn. The operation of Y leaves H dependent on the anode current of a pentode V. Relay A completes a charging circuit over a resistance RA for a pair of condensers CA, CMA so that the potential of the control grid of the pentode is decreased from earth in proportion to the waiting time of the first call. When a second distributer joins the queue, relay B connects a second pair of condensers CB, CMB in parallel with the first pair and completes a second charging circuit over a resistance RB. Similar resistances RC .. RJ equal to RA and RB and pairs of condensers the total capacity of which equals that of each of the first and second pairs are connected in circuit by the queue relays C . . J when further calls are queued. Thus the potential of the control grid is decreased at a rate determined by a rheostat NVR and unaffected by the number of queued calls, and when each call joins the queue the potential is. raised by the sharing of the charges on the pairs of condensers with the uncharged pair associated with the call entering the queue to a negative value indicating the average elapsed waiting time. When the control grid potential falls to a predetermined value representing an average waiting time of say 0.1 minute, the decreased anode current becomes insufficient to hold H which releases, followed by HA and X. Relay HA completes a circuit for the first relay AT of a counting chain AT.. JT. AT locks up, lights an indicator lamp ATL and connects the common terminal pp of the condenser pairs to the first tapping of a potentiometer ATR ..JTR, which raises the control grid to earth potential, so that the original charging conditions for the condensers are maintained, while the voltage across the primary condenser CA remains proportional to the average elapsed waiting time. Relay AT releases Y and relays H, HA, X reoperate in turn. A similar cycle of operations involving the next unoperated relay in the counting chain results from each operation of H, additional lamps being lit to indicate the average waiting time. When an operator is prepared to deal with a call she causes ST to be. temporarily operated. Queue relay A falls back and the first distributor hunts for the marked connecting circuit. The remaining queued distributors take one step forward, each queue relay releasing and, except the lastoperated, reoperating in turn, the release lag of the relays being such that each reoperates before the next release. Each queue relay when released discharges the associated secondary condenser CMA, CMB .. , and the release of the last-operated queue relay disconnects and discharges the corresponding pair of condensers. 'The capacities of the secondary condensers CMA, CMB ... are and so on where c equais the total capacity of each pair of condensers. Thus, assuming the calls have entered the queue at equally spaced intervals and the call leaves the queue just before another is due to enter, the resulting voltage across the primary condenser CA is proportional to the theoretically correct average waiting time. When the average waiting time falls past the value at which the last-operated counting relay operated, the increased anode current temporarily brings up relay L. LA follows to release the last-operated counting relay by energising an opposed 'winding, whereupon the lamp indication is corrected and the potential of the terminal pp is lowered.