Patent GB-693369-A (GB)
Title: Improved means for recording the readings of an instrument or group of instruments
Inventor: MEADOWS STANLEY GEORGE
IPC: H04L23/00
Filed: 1950-06-27
Abstract: 693,369. Selective signalling. SOUTHERN UNITED TELEPHONE CABLES, Ltd. June 27, 1951 [June 27, 1950], No. 16035/50. Class 40 (i) [Also in Groups XVI, XIX and XXXVII] information represented by the position of a measuring instrument is typed in numerical form with the aid of an electric selective system. The invention may be applied to recording the readings of voltmeters or pressure gauges at regular intervals, but,. as shown, is used for recording the unbalanced capacitances between a number of telephone circuits. The receiving instrument is a typewriter which is generally of standard kind and can be used for typing information on the record sheet from a normal keyboard. It is modified only in that (a) the spacing and certain type bars are coupled to actuating magnets; (b) the paper carriage carries wipers W1, W3 co-operating with bank contacts as shown in Fig. 6A, and additional type units for printing two numerals in a single operation are provided. The system illustrated provides for the measurement of 11 capacitances 34, Fig. 6A, in turn, the values varying from + 124 to -124. Each capacitance is allotted six printing positions on the typewriter. The capacitances are measured with the aid of a bridge having coarse and fine balancing capacitors CA, C, each of which is adjusted to add or subtract an element of capacitance by a mechanical coupling with corresponding multi - position switches AV1 ... AV3, Figs. 6D, 6C, and W4 ... W7, Figs. 6B, 6C, one step of the coarse switch corresponding to 25 steps of the fine switch. Detailed operation. According as the coarse switch has remained in its zero position or has been moved one or more steps, relay R or one of relays N, O, P, Q, is operated. Relays O and Q also energizing relay L. Assuming that the typewriter is in the proper position and that the positions of the coarse and fine switches are not inconsistent, relay KMR operates over bank W4 and unlocks the printing key K1, Fig. 6A. When this key is operated, magnet LM operates and locks, energizes SA and brings wipers W5 ... W7 into contact with their terminals (only W4 having been effective hitherto). LM also grounds the terminal encountered by W1 in positions 2 and 3. If the fine switch was set in the direction to add capacitance, the current of KMR included relay A which connects up the printing magnet for the + instead of the - sign. If the measured value exceeds 9 (+ or -) the printing magnet for the sign is energized at once from wire 43 either via wiper W5 and contact R6 or via wiper AV2 of the coarse switch. If the value is less than 10, the spacer magnet MS is energized instead. In either case the paper carriage moves on and 44 is connected to ground instead of 43. Each bar operated releases SA at 22/23 to open the circuit of the type bar operating magnet, but SA pulls up again when the carriage moves on. In position 2, the spacer magnet is energized in all cases and the paper carriage moves to position 3 in which wire 45 is grounded in place of 44. If the + or - sign bar operating magnet has not been operated, it is operated now. If it has been operated, LO has been operated and locked to wire 50 and a circuit is made via 66 and wiper W6 for one of the operating magnets in dependence jointly on the position of the fine switch and the condition of relays O ... R. The carriage then moves to position 4, in which W1 no longer encounters a grounded terminal, and LO and KMR are unlocked. LM, however, remains locked over W2 and provides the operating ground for SA. In this position, a further character, depending on the position of wiper W7 and the condition of relay L, is printed. In positions 5 and 6 a zero and a space respectively are printed and the carriage moves to position 1 of the next group, releasing LM. The value of the next capacitance is similarly recorded in the next 6 positions and so on.