Patent GB-755419-A (GB)
Title: Improvements in or relating to timing circuits
IPC: H04M3/12
Filed: 1954-02-26
Abstract: 755,419. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. Feb. 26, 1954 [March 5, 1953], No. 17554/55. Divided out of 755,335. Class 40 (4). The persistence of various conditions in an exchange system is timed by a circuit comprising memory elements, an element being marked at the first timer enabling pulse following detection of the condition to be timed and another element being marked at the coincidence of an output from the first-mentioned element and a further timer enabling pulse. Single condition; first embodiment. Lines 1013 are scanned by a capacitative scanner 1014 driven in synchronism with a magnetic drum 1010. A circuit 1020 delivers a timer enabling pulse lasting for one rotation of the drum every S seconds. The presence of the required condition on a line causes monopulser circuit 1018 to pulse logic circuit 1019, which also receives a write synchronization pulse and a timer enabling pulse from circuit 1020. If the condition persists until the next timer enabling pulse occurs, so that all three pulses are present, 1019 causes a dot to be entered in the appropriate element of channel 1011 in the manner described in Specification 693,157. At the next rotation of the drum the dot generates an output pulse which passes to a second AND circuit 1030. If the condition persists so that this output pulse coincides with a write synchronization pulse and the next timer enabling pulse 1030 energizes to enter a dot in the appropriate element of timing ended channel 1012. At the next rotation of the drum this dot energizes work circuit 1036 to indicate to an appropriate circuit that the timing period has ended with the condition still on the line; 1036 also pulses circuit 1043 to erase the dots in both channels. If, however, the condition does not persist until the second timer enabling pulse occurs, the detector circuit 1015 causes inverter 1040 to erase the dot in channel 1011. Second embodiment (Fig. 4, not shown). For greater accuracy or for timing longer intervals a larger number of channels may be used. For example, a timer started mark may be entered in channel A, the next timer enabling pulse may erase the mark in A and enter a mark in B, marks being thus entered into a number of channels in binary code. When the desired time has elapsed as indicated by marks in appropriate channels occurring simultaneously, a work circuit energizes as previously described. Several conditions. Several mutually independent conditions on a given line may be timed for different intervals. A separate lead 1070, Fig. 5, for each condition extends from the condition detector 1015 to a coder and writing/erasing control circuit 1072 to write the particular condition in one of a series of channels 1074. These marks are read on subsequent rotations of the drum to be applied to a memory decoder 1075 and a change detector circuit 1076. The next pulse from the appropriate timer enabling pulse circuit 1200, 1201 or 1202 enters a mark in timer started channel 1082. If the condition persists this mark combines with the next pulse from the same timer enabling pulse circuit to enter a mark in the time completed channel 1090. To prevent erroneous marking, change detector 1076 is disabled by inverter 1085 during a timer enabling pulse. Code indication for a number of lines. By connecting a number of lines to a rectifier network, Fig. 6, it is possible to use a smaller number of channels 1074 to indicate the condition of the lines, on entry or erasure from any one of the channels indicating to a change detector (Fig. 7, not shown), the change and the line concerned.