Patent GB-1041293-A (GB)
Title: Communication systems
IPC: B63H3/04
Filed: 1964-01-09
Abstract: 1,041,293. Electric selective signalling. RAYTHEON CO. Jan. 9, 1964 [Jan. 14, 1963], No. 1102/64. Heading G4H. In a data transmitting system a group of four binary bits representing a number from 0 to 15 is converted to a pair of pulses of variable amplitude (termed a " couplet ") the energy of each couplet being the same. The transmitter, Figs. 4a, 4b (not shown), comprises a shift register 24 into which the data groups are entered serially, being read out in parallel by gates 26 by quarter-rate clock pulses from counter 70. The four bits in data-store are converted in diode network 30 to a single marking on one of sixteen leads. The corresponding values 0-15 are coded as a series of vectors, Fig. 2 (not shown), the X and Y components being transmitted as a couplet. For example, the value "5" has X, Y components of - 0-383 and + 0À924, Fig. 3 (not shown). The marking on one of sixteen leads entering gating unit 32 is converted by pulses on leads 35 and 37 into successive pulses on two of thirtytwo leads, in this case leads 5X and 5Y. Of these leads some are to have the same signal value and they are grouped accordingly by OR gates 34-48. For example, the 5X value (- 0À383) occurs also in 11X, 9Y and 15Y. Gate 48 connects all these leads to a unit 64 which provides + 0À383 volts and inverter 65 produces the negative signal. Positive values from units 50-56 and negative values from invertors 59-65 are applied via resistors 74-88 to the transmitter for transmission over a line or by radio. Receiver.-The couplets, Fig. 3, are received in succession with no gap between and a false pair consisting of the second pulse of one couplet and the first pulse of the following one is distinguished from a true couplet by the fact that the energy of all couplets is the same. The incoming couplet signals are applied to a delay device 130, Fig. 6a (not shown), so that the X and Y signals are simultaneously available. The signals are also inverted at 126 and applied to delay line 132 so that-X and -Y are simultaneously available. To distinguish couplets from false pairs, the X and Y signals are squared at 134 and 136 to obtain power and summed at 140. After passing through gate 142 the total energy signal is applied to delay line 144 and comparator 146 compares the energies of successive couplets. A false pair gives a difference signal which is used to reset flip-flop 124. Clock pulses for successive pairs and couplets are obtained by differentiating the incoming signal at 102 and doubling the resultant pulse train. Flip-flop 124 cancels pulses relating to the false pairs so that clock pulses on line CC relate only to the couplet pairs. In Fig. 6b (not shown), the X and Y and inverted signals are connected to resistors 156-170 having values such that when added in pairs in amplifiers 148-154 only one signal is positive. This identifies one of sixteen leads, the marking being gated by the clock pulses on lead CC so that only markings corresponding to couplets are applied to diode re-coder 172 from which four binary bits are entered in store 174. Instead of reconstituting the clock pulses as described, they may be directly transmitted by the transmitter by a second line or wireless channel.