Patent GB-701687-A (GB)
Title: Electrical test equipment for use in telecommunication exchange systems
IPC: H04Q3/42
Filed: 1950-05-05
Abstract: 701,687. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd- May 5, 1950 [June 21, 1949], No. 11162/50. Class 40 (4) In electric test equipment for use in telecommunication systems for testing the circuits of a plurality of groups a set of different test signals greater in number than the total number of circuits is allocated to the circuits and a plurality of different test signals is allocated to each of one or more circuits. As described the test signals are potential pulses in time positions of a cycle, ten such pulses being allocated to each of the 100 outlets of a group selector. The ten time positions of any one outlet occur successively in a period which is characteristic of that outlet. The register-controller is connected to a pulse source producing pulse in the 1st, 2nd, ..., 10th time positions of each such period, each such time position characterizing a group of outlets. Circuits are arranged in groups merely by connecting up the relevant time position pulse source to the outlet. All outlets are scanned but the test equipment responds only to idle lines to which pulses in the relevant time position are assigned. Detailed description.-The embodiment comprises the testing circuits of a group selector which hunts in a group of outlets under the control of a register-controller. Each outlet is represented by its test lead (TL111), the busying contact (BC111), and a marking connection (°1). The outlets are divided into sets of equal numbers and the test leads of the corresponding outlets of each set are multiplied to common points JP1, 2, 3, these points then being multipled to the grid of valve AV. Electrical current gates comprising rectifiers are provided in the leads and are controlled by sources of potential pulses P10-1, P10-2, P10-3 and Pu1, Pu2, Pu3 (Fig. 2) so that the paths between the test leads and the grid of AV are effective in turn cyclically in the order outlet 1 of set 1, outlet 2 of set 1, . . ., outlet 1 of set 2, ..., outlet 3 of set 3. The pulse sources P10 and Pu used for this purpose normally provide a potential of -24 V. and during an impulse OV the arrangement being such that when all the impulse sources connected to a test lead/grid path simultaneously provide OV then AV is conducting. Assuming that ten sets of ten outlets are provided there will be ten P10 sources, ten Pu sources and ten Ï sources and during the period of the PÁ pulse when a path is in this condition the outlet if idle will be connected to a ° impulse source and may produce a Ï impulse in any one of ten time positions. Each ° time position is. allocated to a group of outlets and the corresponding Ï source is connected to the test lead of each line in that group. The group to besearched is determined by the wiper sc in theregister which is connected to the relevant Ï source, say Ï2. Each free outlet provides. an impulse to the grid of AV which is retransmitted over common wire RVL to the grid of TV in the register. This grid is also connected to wiper sc and will be at -24V except during- the Ï2 impulse period so that Rc1 will be non- conductive and the impulse cannot reach the grid except when it is a °2 impulse. Similarly if no impulse is received in the Ï2 periodcurrent flows from sc to -24V. at T1 and the grid remains biassed back. Thus the valve TV will conduct only for outlets in the second group. Then VR fires and relay TR pulls up to register the fact that a free outlet has been found, and an impulse is applied to wire FL which terminates in the se ector. The sets of cold cathode tubes Va, Vb, which are enabled by relay Z (not shown), are controlled by two sets of pulse sources Pu and P10 having similar time positions and durations to those already described but producing different voltage outputs as indicate in Fig. 2. An impulse is thus applied to FL in the time @ in which a certain Pu pulse and a certain P10 pulse corresponding to the outlet selected occur and the relevant Va and Vb tubes fire. The operation of the corresponding Land O relays mark the lead of the selected outlet. The impulse on FL also fires Vc and as a result the grid of AV is maintained at about -25V. to prevent selection of a second outlet. Specification 701,738 is referred to.