Patent GB-337007-A (GB)
Title: Improvements in or relating to the electrical supervision of the position or condition of apparatus at a distance
IPC: H02J13/00
Filed: 1929-07-22
Abstract: 337,007. Automatic Telephone Manufacturing Co., Ltd., Burns, G. A., Rayner, T. R., and Erickson, A. E. July 22, 1929. Selective signalling systems.-In a signalling system a two-wire circuit is used for telegraphic signalling, for the transmission of meter-readings, circuit breaker and tap change switch positions and for telephone communication, the actual signal selected being dependent on the point of division of a cycle of a fixed number of impulses. the impulse trains being of different voice frequencies, if repeaters are included in the circuit, or of direct current of different polarity if a full metallic circuit is provided. If voice current frequencies are used a signal is first transmitted over the circuit to prepare the circuit at the incoming end for reception, this signalling current being maintained on the circuit throughout the connection. Alterations in the position of tap change or circuit breaker positions at a substation are signalled at once to the central station, these signals breaking in on meter reading transmissions should one be in progress. Specification 337,063 is referred to. General operation. To obtain a meter reading an attendant at the central station operates a relative key at the central indicator board CIB which marks a particular contact on the central control group switch CCG and the switch is caused to step. After allowing time for the valve at the sub-station to become heated, voice frequency pulses are sent from CVF to SVF where they are amplified and rectified and cause switches at the sub-station to connect with the appropriate Midworth meter instrument MID. Pulses of voicefrequency current are then sent back from MID to indicate on the mechanical meter MM the required meter reading. The attendant restores the key to normal releasing the apparatus. If a circuit breaker or tap-change switch should change its position one of the latching relays in the group ILR would change over causing the sub-station control switch to make a complete revolution. Switches at the main office step with the suboffice switch and the relays of the locking group 2LR are set to coincide with the relays at 1LR, and to record by means of lamp signals on CIB the position of the circuit breakers and tap change switches. Should a meter reading be in progress when a circuit breaker changes its position, the reading is suspended until the circuit breaker indications have been recorded when the meter reading is allowed to proceed. Telegraph signalling of predetermined instruction from the main to the sub-station is effected by moving the head switch CTH to the required signal. Impulses under control of CCG are transmitted to the substation, where a signal lamp is lit opposite the instruction. The sub-station attendant moves the rotatable arm of his telegraph head switch STH to the position corresponding to the instruction whereupon a check signal is transmitted back to the main office. The restoration of the switches CTH, STH restores the apparatus to normal. Telephone facilities between the two stations is also provided. Meter readings; selection of meter. The Figs. 1 - - 15 of which Figs. 1 - - 8 represent apparatus at the sub-station and Figs. 9 - - 15 show apparatus at the main office should be arranged as one Figure as shown in Fig. 15A. To obtain a reading of a meter, say No. 2, at the substation the key 2, Fig. 13, is depressed which, at the left-hand springs, extends earth to contact 9 of the bank of CSS (Fig. 12) wiped by 1a and at the righthand springs completes a circuit over TPK and conductor 12 to relays X and U (Fig. 12) in parallel. Relays X and U pull up enabling relay LF in the voice frequency equipment, Figs. 10 and 11, to energize. The voice frequency equipment supplies frequencies of 300, 600, and 1,400 cycles, over leads 14, 15; 27, 28; and 34, 35 respectively. The currents being fed to the hybrid transformer XF4 over filters 360LP, 900LP and 900HP. The operation of relay LF feeds current of frequency 300 over the junction 16, 17. At the sub-station the 300 frequency current is induced into the secondary winding of 1XF4 whence it is amplified and rectified by valves 18, 19 and enables 1RL to operate, energizing relay LO, Fig. 4. Relay LO completes a circuit over conductor 24 for the filament circuits of valves 29, 30, 36 and 37 and energizes ITO to disconnect the telephone equipment. The relays at the substation and SL, SM, SH at the central station are connected in series with the filament circuits and should any of the filament circuits be faulty the relative relay would not energize and an alarm would be given. At the main station relay U has energized and this relay completes circuits for relay VA and for magnet CSM of switch CSS and prepares a circuit for relay B. When VA pulls up, V energizes breaking the circuit to relay U and energizing magnet MCM of meter connect switch MCS. Relays V, VA and U interact stepping switches CSS and MCS, and as the relays V. VA and U are slow the rate of stepping is relatively slow allowing time for the valves at the sub-station to become heated. When the wiper 4a of CSS reaches the commoned contacts, impulsing to the sub-station begins and relay VA locks up to speed up the impulsing. When relay U again energizes, MF (Fig. 11) is operated over wiper 4a (Fig. 12) removing the short-circuit across 27, 28 to send a pulse of 600 frequency current to the sub-station. This pulse is accepted by filters 400 HP and 900 LP (Fig. 6), is amplified and rectified by valves 29, 30 and energizes relay 1RM. Relay L (Fig. 4) is operated completing circuits for relay G and magnet SSM (Fig. 2). When relay U releases switches CSS (Fig. 12) and MCS (Fig. 14) make a further step, MF de-energizes cutting off the 600 frequency current supply and allowing 1RM and L at the sub-station to fall away and SSS moves one step. This interaction continues stepping CSS, MCS and SSS until wiper 1a of CSS reaches the marked contact 9 when SW operates. Relay SW locks up, breaks the circuit to MCM and changes over the circuit from wiper 4a from relay MF to relay HF. The switch MCS remains in this position but CSS moves on as U and V continue to interact, relay HF operating with relay U to send pulses of 1,000 frequency current to the sub-station to operate relay IRH. Relay AA now steps in unison with the pulses holding relay G energized and stepping switch SCS. At the main office interaction between U and V continues until CSS steps onto its 24th contact breaking the circuit of U over 2a and energizing MR over 4a. Relay Y is held energized over 4a during impulsing to short-circuit the 600 and 1,400 frequency receiving valves. Relay MR completes a circuit to heat up the receiving valves and prepares circuits to the driving magnets of the mechanical meter MMT. At the sub-station relays G and GA release and during the slow release period of GA, CO (Fig. 3) operates completing a circuit for H (Fig. 1). The bank wiped by 4a of switch CSS (Fig. 12) is so wired that 17 impulses are always transmitted to the sub-station, the impulses being in two sets having different frequencies the number of impulses in the sets depending on the terminal marked in 1a. In the example described two impulses of 600 frequency and 15 of 1,400 frequency would be transmitted setting switch SSS (Fig. 2) into its 3rd position. and switch SCS (Fig. 1) into its 16th position. The wiring between banks 1c and 2d of these two switches is such that a circuit is only completed if the full 17 impulses have been received and in this case relay H operates completing a holding circuit for CO, energizing SA, preparing circuits for D and K and energizing IMS (Fig. 5) to connect up the Midworth power instrument (not shown) whose pointer is mechanically linked with the movable pointer 42 or MID1. Transmission of meter reading. The field circuit 43 of MXU is energized and motor 46 drives, its direction depending on which contact of fork 45 the pointer 42 is engaging. The motor drives the slider 47 over the resistance to adjust the current in the coil of MIDI and when balance is reached the pointer will be suspended between the contacts and the motor circuit opened. The coil 48 of PWR is connected in series with and will tend to take up the same relative position as the coil of MIDI and its pointer 51 consequently makes contact and enables the motor 53 to drive the pointer into a position of balance. Geared to the motor is a cam wheel 54 which moves springs 55 to operate relays D and K for the transmission of impulses to the central station, a pulse of 1400 frequency being transmitted back during the slow release period of K at each step. This pulse operates relay RH, Fig. 11, and relay 2B pulls up, energizing magnet A of MMT (Fig. 15) to step the meter one step. The meter comprises two ratchet and pawl mechanisms driven by magnets A and B respectively, which drive the pointer in opposite directions. If the power instrument at the sub-station had moved in the opposite direction, the pointer 42 would be in contact with the other fork of 45 and 53 would have driven the cam-wheel 54 in the opposite direction (which is assumed to be anti-clockwise). The arm 68, friction tight on spindle 69, would have operated springs 72 and energized relay RV. Relay RV transfers the impulses controlled bv K and D from IHF to IMF and consequently pulses of 600 frequency would be transmitted to line to energize relay RM at the main station. Relay RM repeats the impulses to IB (Fig. 14) which controls magnet B of MMT to drive the pointer 67 in the reverse direction. A separate meter MMT is provided for each of the meter keys, connection being established over separate terminals of the banks wiped by 2h and 3b. When the meter reading is complete the meter key is released completing homing circuits for MCS over 1b and CSS over 3a. Relay X releases deenergizing MR and LF, which latter relay re-