GB1175102A - Pest Repelling System - Google Patents

Abstract

1,175,102. Acoustic signalling. T. B. SHAW. 13 Feb., 1967, No. 6836/67. Heading G4F. [Also in Divisions A1 and H4] A pest repelling system (Fig. 1) comprises spaced transducers 20, 22 &c., for emitting audio frequency energy, an electrical signal generator 10, an amplifier 14, and a gate 12 arranged intermittently and automatically to interrupt delivery of signals by the amplifier 14 to supply bursts of signal energy to the transducers 20, 22 &c. Circuit.-The oscillator 10 comprises two transistors 38, 50 (Fig. 2) and a feed-back path through series connected resistor 60 and capacitor 62. An adjustable inductor 40 and a capacitor 42 are provided. The output is supplied to an amplifier stage 68 through an astable multivibrator (12) comprising NPN transistors 70, 72 alternately switched on and off for gating periods of approximately two seconds. The amplifier 14 (Fig. 1) includes an amplifier stage 68 and a mixer amplifier stage 108 added to the stage 68 in order to supply the drive signals supplied to the output amplifier of an expanded system. A switch assembly 110 in one position connects the output of transistor 68 to transistor 104 in a driver circuit 16 and in the other position disconnects the output of the transistor 94 from the transistor 104 and connects it to the transistor 106. A transformer 124 has a plurality of secondaries 126 operative to feed a plurality of driver components with a driver signal similar to that of the driver circuit 16. The driver circuit 16 includes an output transformer 128 (Fig. 2a) coupled, through a capacitor 130, to the emitter of transistor 104. Associated with each driver circuit 16 is an amplifier 18 comprising class B operating transistors 132, 134. The amplifier 18 is rendered operative by closing a switch 150 associated with the transducer jacks 152, 154 and thereby rendering a resistor 148 effective. The jacks 152, 154 are respectively in parallel with the secondary 156 of an output transformer associated with an amplifier stage 24 including transistors 160, 162. A voltage is applied to interconnected centre taps of the transformers by closing a switch 170 on plugging into the jack 154 so as to render amplifier stage 24 operative. At the same time voltage will be supplied to a pilot lamp 172. The output transformer 140 has three secondaries 166 to which similar output amplifier stages 24 are connected and a secondary winding section 174 to which a pair of parallel connected transducers 20, 22 are connected.