Patent GB-551328-A (GB)
Title: Improvements in or relating to telecommunication exchange systems
IPC: H04M15/08
Filed: 1941-08-15
Abstract: 551,328. Automatic exchange systems. STANDARD TELEPHONES & CABLES. Ltd., and HAIGH, L. B. Aug. 15, 1941, No. 10399. [Class 40 (iv)] In an identifying system, the lines are connected over isolating condensers or rectifiers to two groups of points, all the lines having the same thousands and hundreds digits being connected to the same point in one group and all those having the same tens and units digits being connected to the same point in the other group. Each of these common points is connected to two further points which may be switch contacts or discharge tube electrodes and are special to the respective digits characterizing the common points. The arrangement may be as shown in Fig. 8 in which an identification control circuit ICC causes the application of a unidirectional marking voltage to the third wire of the established connection thus marking appropriate terminals in the bank of a switch IF which is caused to advance and to control the charging of the condensers of four condenser registers when it encounters the marking potential. The records of these registers are transferred to the circuit ICC in known manner. Other arrangements are described in which the switch IF is replaced by four switches which stop on encountering a marking potential thus registering the digits by their position. In other arrangements the switches are omitted, the registration being effected with the aid of four groups of ten discharge tubes connected up simultaneously or one group of ten discharge tubes connected to the marking wires for the respective digits by relays in succession. The circuit ICC may be associated with the junction instead of as shown. Arrangements in which a marking applied to the line circuit from a point ahead is sought by a hunting switch. In the arrangement shown in Fig. 1, each meter-wire is connected through an individual rectifier RA to a point which is common to all lines having the same thousands and hundreds digits and an individual rectifier RB to a point similarly shared with the lines having the same tens and units digits. Connections from these points are distributed over the ten banks of a 40-position. switch, any particular point of one group being connected in the bank corresponding to the value of the hundreds digit to the terminal in the first ten corresponding to the value of the thousands digit and in the bank corresponding to the value of the thousands digit to the terminal in the second ten corresponding to the value of the hundreds digit. The points for the tens and-units digits are similarly connected to the third and fourth sets of ten terminals. When a line is to be identified, a low voltage + battery is connected to its meter wire and the 40-position switch, ten wipers of which are connected via isolating rectifiers to the. control. electrode of a cold cathode discharge tube, is started up. In positions in which the identifying marking is picked up the tube breaks down energizing relay TR which stops the switch and charges a register condenser connected up over an 11th wiper. The switch is then moved on automatically by means not shown, the tube is extinguished and TR falls back and subsequently responds to the next digit-marking. The number is transferred from the register to the ticketing equipment or number indicator in known manner. The condenser register may be replaced by 4-relay registers, Fig. 7 (not shown). In a modification, Fig. 2 (not shown), the switch does not stop on the marked contacts and has means for discharging the register condensers that do not correspond to marked positions. In another modification, Fig. 3 (not shown), separate 10-position switches hunt simultaneously or successively for the markings and register the number by the positions in which they stop. They can also be made to control the transmission of impulses as they are stepped home in succession from the marked positions, the initial setting preferably being to a position complementary to the value of the digit concerned. In another arrangement, Fig. 6 (not shown), an alternating current marking is applied to the meter wire of the line to be identified and condensers are used instead of the rectifiers RA, RB. To avoid interference of the thousands/hundreds identification by the tens/units marking and vice versa, all the marking wires are normally grounded, the ground connection of the thousands/hundreds wires being removed only during the corresponding hunting operation. The A.C. marking is detected by a thermionic valve instead of a cold cathode discharge tube. In this arrangement also, four switches can be used in place of one. Transfer of number to register without the use of hunting switches. As shown in Fig. 4, there are 40 cold cathode discharge tubes, one for each of the values of the four digits, common to the whole office, and connections are made to these through isolating rectifiers such as RC12, RD12 from thousands/hundreds and tens/units wires associated with the meter wires as in the previously described arrangements. When an identification is to be performed, relays ST in a particular identification circuit is energized and provided that no other identification equipment is using the discharge tube equipment, TR and L pull up energizing THZ, HZ, TZ, UZ for an instant the length of which is determined by the operating line of a sluggish relay SO. UZ applies a marking to a point in the established connection and the appropriate tubes break down charging the corresponding register condensers. SO on operating releases all the operated relays except ST and locks up until ST is released. In a further modification, Fig. 5 (not shown), the same ten discharge tubes common to the whole exchange are used for all four, digits, being connected up in succession between the marking wires and the registers by a relay chain. Specification 539,823 is referred to.