Patent GB-701523-A (GB)
Title: Selection systems for electric circuits or equipments
IPC: H04Q3/00
Filed: 1950-11-17
Abstract: 701,523. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Nov. 17, 1950 [Nov. 24, 1949], No. 28190/50. Addition to 653,524. Class; 40 (4) In a two-stage group selector of the type claimed in the parent Specification, which comprises primary selectors each giving access to a plurality of secondary selectors, each of which in turn gives access to a plurality of outlets leading in different directions, and in which a primary selector will select a secondary selector only if the latter has access to at least one free outlet in the wanted direction, provision is made of control means associated with a secondary selector and controlled means associated with a primary selector, the control means operating when the secondary selector has seized a free outlet'in the wanted direction and causing the controlled means to complete the connection from the primary selector to the secondary selector. Provision is also made of retardation means coming into use immediately after the selection of a secondary selector and until the selection of'an outlet thereof, and which operates after a delay period if the following operations do not take place in the usual period, whereby the group selector is restored to normal and primary hunting is resumed. Common control circuits are provided for the primary and secondary selectors respectively and selection control equipment in the common control circuits transmit selection signals which each consists of an electrical impulse occupying an individual position in a recurring cycle of time positions, different selection signals being used for the primary and secondary control circuits, the register-controllers including means for exercising control in response to the selection signals from the primary and secondary control circuits at different times. Primary hunting:-It is assumed that the primary selector Se1 (Fig. 2) has been seized by the preceding selector Se (Fig. 1) and that a register-controller En (Fig. 1) has been associated over finder Ch. Ground applied to wire b by the register-controller completes a series circuit for the right-hand winding of the clutch. magnet H of selector Se1 and relay A in the primary common control circuit Or1 in which relay A only operates. The consequent energization of Band C enables the scanning device Ex and the indicator In. The operation of the scanning device, which has been described in Specifications 698,802 and 700,088, results in impulses being sent over the wire d, in each of the time units characterizing a free secondary selector Sell giving access to at least one free line in the group scanned. These impulses are sent during the time of transmission of impulses Pa1 and Pa3 (see Fig. 3) provision being made to scan up to 50 outlets of Se1. In the register-controller the impulses are received by comparator Co to which are also applied impulses PN characterizing the group of outlets desired. When there is coincidence between an impulse from Or1 and the comparison impulses PN and Pal or Pa3 the comparator operates as described in Specification 700,088, producing an impulse in the middle winding of TR (Fig. 1) which is induced into the two other windings. This impulse, which characterizes the secondary selector to be selected, fires tube T1 and operates relay Si and is also sent over wire c to the indicator In of the primary common control circuit Or1, where as described in Specification 700,088 it causes the firing of a combination of tubes (not shown) characteristic of the impulse. The resulting energization of a combination of relays such as O causes the operation of the vertical magnet V relevant to the outlet to be selected, which locks up in series with relay M. The scanning device is blocked and no further impulses reach the register-controller. The operation of Si (Fig. 1) brings up Do, whereupon Tl is extinguished, Si releases, and Do locks up in series with Eo. The operation of M (Fig. 2) releases B and C commences to relapse. On the operation of V, G pulls up and, provided the secondary selector Se<SP>1</SP>1 has not been selected by another primary selector, locks up in series with K. The indicator In returns to normal and the relays O are released. Secondary selection:-Relay K holds M and V independently of the O relays ; completes a series circuit for clutch magnet H<SP>1</SP> and relay A' in which A' only operates (B<SP>1</SP> following) ; and extends wires c and d to c<SP>1</SP> and d<SP>1</SP> respectively. With B<SP>1</SP> up the scanning device Ex<SP>1</SP> sends impulses over wire d<SP>1</SP> in each of the time units characterizing a free outlet of selector Se<SP>1</SP>1. These impulses to a maximum of 50 are sent during periods Pa2 and Pa4. In the register-controller the comparator Co is now conditioned to respond to these impulses (Eo up) and on the reception of an impulse characterizing an outlet in the desired group operates as in the primary selection. T1 is fired and an impulse is sent forward on the wire c to operate a combination of tubes (not shown) of indicator In<SP>1</SP>. The operated relays O<SP>1</SP> bring up the relevant magnet V<SP>1</SP> which locks up with M<SP>1</SP> and the scanning device Ex<SP>1</SP> is blocked. In the register-controller the re-operation of Si brings up Fo which connects up test relay T. If the outlet is free T operates and shunts its high resistance winding by Dt (which operates) whereupon K<SP>1</SP> comes up in series, holds M<SP>1</SP> and V<SP>1</SP> and releases B<SP>1</SP> which is followed by the O<SP>1</SP> relays. The outlet is marked busy by the application of battery to..back contact HB <SP>11</SP>5 through the low resistance windings of relays T and Dt in series with K<SP>1</SP>. Switching through:-The operation of Dt (Fig. 1) brings up Ok which short-circuits resistor rl to energize clutch magnet H, releases Si and extinguishes T1. Relays Do, Eo and Fo relapse. Magnet H locks up over wire e and completes a series circuit for relays E (Fig. 2) and Fr (Fig. 1). Relay E operates, short-circuits r5 to energize clutch magnet H<SP>1</SP>, and brings up F. The latter relay holds K and G and removes the short-circuit from the right-hand winding of C which releases rapidly but without effect. Magnet H<SP>1</SP> completes a series circuit for E<SP>1</SP> and L whereupon E<SP>1</SP> operates and brings up F<SP>1</SP> which short-circuits the upper winding of E<SP>1</SP> thus operating L. The upper winding of E is thus short-circuited and relay Pr (Fig. 1) pulls up. Pr releases T, Dt and Ok, whereupon E and Pr fall away. Relay B energizes servo-magnet SH which displaces the horizontal bar of Sel prepared by magnet H, and releases E<SP>1</SP> which energizes SH<SP>1</SP> in selector Sell. The wires a, ..., d are thus extended to a<SP>11</SP>, . . ., d<SP>11</SP>, and the common control circuits are disconnected by contacts HB1 to HB4 and RB1<SP>1</SP> to HB4<SP>1</SP> and are released in known manner. Magnets H and H<SP>1</SP> remain held over their left-hand windings. Selection of same secondary selector by two primary common control circuits. In such a case at least one relay G cannot be held and the corresponding relay K remains down so that on the release of relays O relay M relapses to re-operate B and allow scanning by Ex to re-commence. Relay Bo (Fig. 1) is short-: circuited as soon as primary hunting ends (Eo up) and after its slow release Do and Eo fall away. Bo then re-operates and the primary hunting is repeated. Selection of same outlet by two secondary common control circuits. Two registercontrollers are connected in parallel to the same outlet so that at least one relay T cannot be held and the corresponding relays Dt and K<SP>1</SP> remain down. Relay M<SP>1</SP> is released, BI re-operates and scanning by Ex<SP>1</SP> re-commences. Bo is short-circuited as soon as the secondary hunting ends (T back, Fo up) and after its slow release Do and Eo fall away. Fo and Si are released and T1 extinguished. In the primary common control circuit C has its circuit opened as soon as the primary hunting ends (B back) and after its slow release K, G, M and magnet V fall away in turn. B is re-energized and re-operates C and hunting re-commences. Wanted group of secondary outlets fully engaged between primary and secondary hunting. The secondary scanning is without result and relay C releases slowly. Bo (Fig. 1) (short-circuited by Eo up) falls away and releases Do and Eo whereupon Bo re-operates. Primary hunting is then re-commenced. Seizure of primary common control circuit during secondary hunting by a second registercontroller and primary selector. The two register-controllers each receive the impulses from the secondary common control circuits but as these are sent during periods Pa2 and Pa4 the second register-controller with Eo down will not respond and false selection is prevented.