GB1145745A - Timing circuit - Google Patents

Abstract

1,145,745. Transistor delayed switching circuits. E. W. BLISS CO. 12 May. 1966 [12 May, 1965], No. 35126/68. Divided out of 1,145,744. Heading H3T. In a timing circuit TM1, a capacitor 22, Fig. 2, is charged upon receipt of an input signal, then partially discharged by means such as unijunction transistor 18 when the charge reaches a predetermined level and finally more completely discharged under control of a bistable multivibrator MM1 actuated by means 18. As described, capacitor 22 charges through resistances 26 and 24 when a normally conducting transistor 34 is cut off by an input pulse; when the voltage across the capacitor is sufficient the unijunction transistor 18 conducts and discharges the capacitor through resistance 30 thereby producing an output pulse across this resistance. In response to this output pulse an external bi-stable multivibrator MM1, Fig. 1, restores transistor 34 to conduction so that the capacitor 22 can complete its discharge through diode 32 and the transistor. This discharge circuit ensures that all the timed periods are equal; without it the first period would be longer than subsequent ones (Fig. 3, not shown) since the capacitor 22 cannot discharge completely through the unijunction transistor 18. Traffic control system.-Each of four signal lamps has associated with it a bi-stable multivibrator MM, Fig. 1, and a timing circuit TM. When the first bi-stable circuit MM1 is set it illuminates the corresponding lamp MSG and starts its timing circuit TM1. The output of the timing circuit sets the bi-stable circuit MM2 of the next phase; this re-sets the preceding bi-stable circuit MM1, illuminates its signal lamp MSC, and starts its timing circuit TM2.