Patent GB-709918-A (GB)
Title: Improvements relating to indicating apparatus
Inventor: TAYLOR MAURICE KENYON
IPC: G08C21/00
Filed: 1951-01-09
Abstract: 709,918. Electric selective signalling. FERRANTI, Ltd. Jan. 9, 1952 [Jan. 9, 1951], No. 583/51. Class 40 (1). A plurality of conductors are adapted to be energised singly, and the conductor energised at any moment is indicated at a distance by sending coded signals representing the number of the conductor in a selected scale of notation of radix n. A number p, of power windings are used equal to the powers of the radix required to represent the highest conductor number, and each power winding is inductively coupled to at least one set of n digit windings representing the digits 0, 1, 2 ..... (n-1). The zero digit winding may however be dispensed with. Energisation of any conductor is arranged to energise in series only those digit windings associated with the various power windings corresponding to the conductor number in the scale in question, and from the energised digit windings the output signals are derived in various ways dependent on the electrical characteristics employed. Where the binary system is used the power windings may be energised at different individual frequencies, in which case the series connected digit windings selected by an energised conductor, cause the frequencies of the inductively associated power windings to appear therein and hence in the output circuit which is series connected with the selected digit windings. Zero digit windings, when used, may induce voltages of opposite phase to the unit digit windings or of different amplitude. A ternary system is also described as well as an arrangement for precluding false transmission. The invention may be used for indicating angular position or linear position e.g. the position of a potentiometer wiper. Transmitter.-As described in Specification 709,910 the position of a stylus 27, Fig. 1, relative to a rectangular co-ordination system 26 is, through pantograph linkages, repeated by electrically connected contacts 19, 23 which engage respectively X, Y conductor bars 14, 17 mounted on opposite faces of an insulating sheet 10. The conductors of each set X, Y are allocated numbers in the binary system as shown in Fig. 2, and are series connected to corresponding digit windings t1a-t1d, t2a, t2b, t3, t4a-t4d, t5a, t5b, t6, on the power transformers T1-T6 having power windings t1p-t6p. The transformers T1, T2, T3 correspond to the powers 2‹, 2<SP>1</SP>, 2<SP>2</SP> respectively for the X conductors 14 and transformers T4 -T6 correspond to the same powers of two for the Y conductors 17. The respective X, Y conductor bars whose point of intersection corresponds to the position of the stylus 27 are electrically connected by their contacts 19, 23 so that the digit windings corresponding to the X, Y binary members so selected are series connected by way of the output CL to the receiver. The power transformers T1-T6 are separately energised by oscillators FS1-FS6 at individual frequencies f1-f6, and a combinations of these frequencies appears in the output circuit corresponding to the digit windings energised and hence to the X, Y binary numbers. Alternatively, a single A.C. source may be connected across the lines 40, 41 at CL, Fig. 5, and individual output channels CL1-CL6, taken from the power windings t1p-t6p to the receiver in which case output currents will be derived from a combination of those channels corresponding to the binary X, Y numbers in question. The output channels may be connected sequentially to the receiver over a single line. The conductors need not be numbered consecutively, e.g. as shown in Fig. 5, where the binary numbers of adjacent conductors differ in respect of one digit only and so preclude false signalling due to bridging of adjacent X or Y conductors by the contacts 19, 23. For transmitting angular position the angular positions of a selector switch, Fig. 6 (not shown), are numbered in the binary system, the number being transmitted in the binary code in the same way as described for Fig. 2 for each of the X, Y positions. Fig. 7, shows the transformers T1-T3 of Fig. 2, on which oppositely wound digit windings t1b<SP>1</SP>, t1c<SP>1</SP> ... &c., are provided on each core so that where a zero digit occurs in any power of the binary number selected, a signal of the same frequency but in anti-phase to the signal for digit 1 in the same power is sent. In another embodiment, Fig. 8 (not shown), the zero digit windings of Fig. 7 are wound in the same direction but with only one half the number of turns of the .unit digit windings so that zero and unit signal elements are distinguished by amplitude. Fig. 9 shows an example using the ternary scale in which the unit digit windings have the same number of turns as the digit windings representing the digit 2 but are oppositely wound. Zero digit windings are not shown but if used the three different digit windings could be distinguished by their number of turns. Receiver.-The receiver, Fig. 4 (not shown), is as described in Specification 709,910, but where angular position is being transmitted Fig. 6 (not shown), the receiver may comprise a circular arrangement of neon lamps corresponding to the selector switch positions, the neon lamp corresponding to the selector position being lighted when a corresponding spark gap in a decoding device is bridged as described in the above mentioned Specification.