Patent GB-820898-A (GB)
Title: Improvements in or relating to telephone systems
Inventor: DENBY JAMES FREDERICK
IPC: H04Q3/00
Filed: 1956-10-30
Abstract: 820,898. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. Oct. 15, 1957 [Oct. 30, 1956], No. 33019/56. Class 40 (4). In a sequence control arrangement, which may, for example, time the successive operations of control equipment in an automatic exchange, a first timing circuit times the duration between the generation of two successive operational signals and a second timing circuit times a period slightly longer than that duration, the two devices being started simultaneously following the generation of one signal, and the generation of the next signal being capable of being effected under control of either device, the generation of the next signal under control of the first device inhibiting the operation of the second device. The arrangement has a number of stages each of which generates an operational signal as it becomes effective and the timing devices, arranged effectively in parallel link the stages. The drawings show two adjacent stages linked by the two timing devices. The first timing device consists of a number of positions each consisting of a cold cathode-tube arranged as a pulse-repeating tube and one other tube arranged as a count tube, the positions becoming effective in turn. Only one position, exemplified by count tube VKSBA or VKSBB and pulse repeating tube VKPB is shown, it being understood that the number of positions included will depend upon the length of the required duration between signals and the recurrence frequency of the pulses from the pulse source driving the sequence arrangement. The second timing device consists of tubes VKTB, VKDB and VKALB, the timing function being performed by the delay network R1, C1, MR1 between the cathode of VKTB and the trigger of VKDB. The pulses are obtained from VKPU which is common to all stages and the H.T. supply of which is in the form of pulses PHT which occur at the rate of 1 ms. on and 2 ms. off. These pulses are repeated to leads 10 and 11, the former being connected to the fault tubes such as VKPPB and VKPPP, and the latter to the pulse repeating tubes such as VKPA, VKPN and VKPB. Normal operation.-This is initiated by the firing of VKSA. If the stage shown in Fig. 1 is the first stage, VKSA will be struck by a pulse derived from and synchronous with a pulse PHT; otherwise the pulse applied to VKSA will come from the last pulse-repeating tube of the first timing device between the stage shown in Fig. 1 and the preceding stage (not shown). VKSA extinguishes the tube in the preceding stage (if any) corresponding to VKSBA or VKSBB, and primes VKPA. The next pulse on lead 11 fires VKPA which pulses VKSBA, VKFAA and VKTB, all of which fire. VKSBA extinguishes VKSA and primes VKPB, whereas VKFAA marks lead A to enable operation A to be performed in the control equipment (not shown), and if the stage is other than the first, applies a pulse to fire VKBA which backs off VKALA, which tube is pulsed over lead 12 from the second timing device of the preceding stage. The firing of VKTB applies potential to the delay circuit R1, C1, MR1. At the end of the H.T. pulse, VKPU and VKPA are extinguished. The next pulse on lead 11 fires VKPB (primed by VKSBA) which repeats the pulse to the next position count tube (not shown) which fires, thus extinguishing VKSBA and priming the next position pulse-repeating tube (not shown). Each successive pulse on lead 11 steps the device on one stage until eventually the count tube VKSN of the last position is fired, extinguishes the previous position count tube, and primes VKPN. The next pulse on lead 11 fires VKPN, which strikes VKSPA, VKTC, and VKFBA. VKSPA extinguishes VKSN and primes VKPP, whereas VKFBA marks lead B to enable operation B to be performed, and strikes VKBB, which backs off VKALB. VKTC applies potential to the delay circuit extending to the next stage. When VKDB eventually strikes it is ineffective as VKALB is backed off. Operation under fault conditions.-If any of the positions between VKSBA and VKSN were faulty and either a pulse-repeating tube or a count tube failed to strike, then tube VKFBA would not fire. Firing of VKDB then fires VKALB, whereupon relay ALB pulls up, fires VKHB and VKFBB, and primes VKPPP. The firing of VKFBB marks lead B and that of VKHB brings up the common alarm relay AL. Tube VKHB remains conducting and relay AL operated until the alarm reset key KAR is thrown. VKPPP strikes to the next pulse on lead 11, followed by VKFPP, which fires VKSPB, whereby VKPP is primed and the conducting count tube is extinguished. On the release of the equipment by the removal of the HT and PHT supplies, all tubes except VKHB are extinguished and all relays. If the equipment is again seized before the fault is cleared, it will again operate under fault conditions, as described above.