GB908794A - Apparatus for generating signals at random time intervals - Google Patents

Abstract

908,794. Pulse generating circuits. COURTAULDS Ltd. Nov. 20, 1959 [Nov. 21, 1958], No. 37489/58. Class 40 (6). A random pulse generator comprises a waveform generator 20 connected to a capacitor 26 by changeover contacts 23 which connect the capacitor 26 alternately to the generator 20 or to a discharging circuit 24 containing a relay which controls further changeover contacts 29. A capacitor 27 is similarly alternately connected to generator 20 or to a further discharging circuit 25 containing a relay which in turn controls changeover contact 23. With the contacts in the position shown, capacitor 26 discharges through relay 24 until the current falls sufficiently to release the relay 24. Contacts 29 now change over, energizing relay 25 from the charge on capacitor 27, so that contacts 23 recharge capacitor 26 from the triangular wave generator 20. The charge on the capacitor connected to the generator 20 will thus be continually varying. The time taken for the capacitor to discharge to the release voltage of the relay is dependent on the initial charge on the capacitor, hence, provided the period of the triangular wave is less than the minimum discharge time, the relays will change over at random intervals. The system shown contains further circuits which result in the frequency, amplitude and duration of output pulses on line 37 varying in random manner. A second triangular wave generator 21 is provided to control the duration of each pulse on line 37. Contacts 30, 32 are respectively operated by relays 24, 25 so that when a signal controlling the start of a pulse is provided by the changeover of relays 24, 25, contacts 30, 32 change over, energizing relay 28 from one of capacitors 31, 36 charged from triangular wave generator 21. Relay 28 remains energized for a time depending on the voltage to which the capacitor has been charged by generator 21. Before relay 28 is operated, lead 37 is fed from a D.C. potential O which determines the base level of the output pulses. When relay 28 is energized, contacts 34, 35 are in the opposite positions from that shown so that the pulse amplitude is dependent on the voltage to which capacitor 33 has been charged by the triangular wave generator 22. Modifications.-Fig. 2 (not shown) relates to a modification in which generator 22 is omitted and a further capacitor is charged from generator 21 and switched by further contacts of relay 28 to a buffer amplifier feeding a further capacitor connected to the left-hand side of contacts 35. A sine wave generator may replace generator 20. Alternatively, three generators of different frequency may be selected in turn by signals derived from the output of the system. The apparatus may be similarly used to derive a large number of random pulses from a small number.