Patent GB-1106691-A (GB)
Title: Supervisory arrangement for pulse trains
IPC: H04M15/04
Filed: 1965-03-19
Abstract: 1,106,691. Automatic exchange equipment. STANDARD TELEPHONES & CABLES Ltd. 19 March, 1965 [26 March, 1964], No. 11731/65. Heading B4K. Metering pulse trains are produced by forming combinations of the basic pulse trains T1, T2, T4, T8, and T16 shown in Fig. 1, an alarm signal being produced if the pulse length or repetition rate of the basic pulses varies beyond a given tolerance and an alarm being produced if the metering pulse trains are malformed. The basic pulse trains are produced by division of a fundamental pulse train. The number of pulses of each train in a period of 11À25 seconds (one sixteenth of a standard 3-minute charge period) is one, two, four, eight and sixteen, respectively. When assessed for metering each metering pulse train is divided by sixteen. To test pulse length and repetition frequency the basic pulse trains are combined in OR circuit OT1. The output of OT1 thereby produced is the fundamental pulse train less one pulse; the missing pulse being supplied from a multivibrator Mv. The leading edges of the resulting fundamental pulse train produce equal valued pulses of 110 ms. duration at the output of a multivibrator Mvk. The equal valued pulses are applied to a charge/ discharge system # 1 /# 2  to produce a sawtooth waveform the D.C. level of which rises or falls with the pulse repetition rate. Should limits be infringed an alarm circuit ABS operates. By balancing the equal valued pulses from Mvk against the fundamental pulses proper from OT1 the widths of pulses can be tested. The balance is made pulse-by-pulse in a bridge A said to contain triodes T9, T10. Out of balance output is amplified at T6 and a delay circuit T masks differences in pulse length of Œ20%, greater differences operating the alarm ABS. Malformation of the metering pulse trains, shown as pulses appearing on terminals VT2, VT3 &c., from a source VG in Fig. 3, can be tested by effecting the combination of the basic pulse trains in a circuit separate from VG and applying that version of the train to one end of a bridge, such as A, and the corresponding train from VG to the other end of the bridge. Outof-balance output is delivered to the amplifier T6 and delay circuit # to operate alarm circuit ABS for discrepancies outside the Œ20% limits. As illustrated, however, the metering pulse trains are tested in groups, each group tested having a respective bridge such as A or B. Considering the group of metering pulse trains VT3, VT5, VT7, and VT9, for instance, the basic pulse component T1 will appear simultaneously at the right-hand side of a bridge over separate metering pulse train leads with respective diodes D1 and resistors W1. To balance this group input the actual basic pulse T1 applied to the left-hand side of the bridge is applied over four resistors W in parallel. The simultaneous appearance of pairs of T2, T4 and T8 pulses, which form the other components of the metering pulse train group, is similarly balanced by connecting the corresponding actual basic pulses to the bridge over resistors W in parallel. Out-of-balance currents operate the alarm circuit ABS, as before, over amplifier T6 and delay circuit T.