Patent GB-901445-A (GB)
Title: Improvements in or relating to pulse-generating arrangements
IPC: H03K5/156
Filed: 1959-01-30
Abstract: 901,445. Pulse generator circuits. SIEMENSHALSKE A.G. Jan. 30, 1959 [Jan. 31, 1958; May 20, 1958], No. 3392/59. Class 40 (6). In a pulse pattern generator a pulse producing two-state device controls a second such device to produce pulses which are not coterminous with the pulses produced by the first device, the two pulses generated are applied to a gate circuit which produces an output depending on the time relation between the pulses applied to it. As shown in Fig. 3, pulses generated by the free-running multivibrator M1 comprising reciprocally coupled PNP transistors control a bi-stable circuit M2 which itself controls a further bi-stable circuit M3 so that pulse trains as shown in Fig. 2, a, b, c, are produced at their respective outputs. The output from bi-stable device M2 and the inverted output from device M3 are applied to an AND gate K1 comprising resistor R3 and rectifier G2 so that the voltage at the junction of R3, G2 is low only when the right-hand transistor of device M2 and the lefthand transistor of device M3 are both in the cut-off condition. The output of AND gate K1 is applied to the base of transistor T1 which with resistor R5 constitutes a modified AND gate S1. The output of gate S1 is negative when the lefthand transistor of device M1 is cut-off at the same time as the output of AND circuit K1 is positive. Thus the output of the gate K1 is a pulse train, Fig. 2d, and of gate S1 the pulse train of Fig. 2, e. These pulse trains may be used as the free and engaged signals, respectively in an electronic telephone exchange system. As shown in Fig. 3, the output from an audio-frequency generator may be applied to the primary of a transformer U2 and switched on and off by gating circuits comprising diodes G3 and transformer U1 so as to produce modulated audio frequency at the output Z1, Z2. Thus transistor T2 which is directly controlled by the inverted output of the bi-stable circuit M2 is associated with transformers U1 so that if either of the transistors is in the cut-off state the rectifiers G3 are not conductive and the transmissions of signals from the generator via transformer U1 is prevented. The transistor T2 associated with output terminals Z2 is controlled by the output of the modified AND gate S1 so that if the transistor T1 is cut-off (output of the circuit K1 positive), the transistor T2 conducts and is cut-off in synchronism with pulses from multi-vibrator M1 so that the alternating audio voltage from generator is transmitted via transformer U2 in the same rhythm to the output terminals Z2. If transistor T1 is conducting, transistor T2 is cut-off irrespective of the state of multivibrator M1 so that the transistor T2 is cut-off after every three pulses delivered by multivibrator M1 and remains cut-off during the fourth pulse. In the modification shown in Fig. 4, five monostable multivibrators M1 ... M5 are connected in tandem each being controlled by the output of the preceding one. The multivibrator M1 has no delay so that a control voltage at its input Z changes it to the " set " state without delay and when the control voltage is removed it returns to the normal state also without delay. The output from M1 in its " set " state causes multivibrator M2 to be changed to its state with a time delay and when multivibrator M1 returns to its normal state M2 returns to its normal state without delay the further states M3 ... M5 also operate as the stage M2. The respective outputs from the stages M1 ... M5 control the operation of AND and OR gates so that a pulse pattern may be generated as required, Fig. 5 (not shown).