Infinity Bug

At this point you whistle into the receiver and the Infinity Bug will pick up the line. The high-gain amplifier in the Infinity Bug will pick up the audio at the place where it is located. It can only be assembled on the PC board supplied in the kit as the Latching Circuit is already soldered to the board and the project will not work with substit
Infinity Bug - schematic

ute components. When the Infinity Bug is connected to the line, the "line voltage" will drop to about 36v, due to the current drawn by the bug. This will not upset the operation of the phone system. The bridge on the front-end allows the project to be connected either way around and allows for the annoying feature of some phone lines. They create a voltage reversal as soon as the phone is picked up and this would defeat a Bug that requires a polarized voltage. The only two sections drawing current during quiescent conditions is the whistle-detecting circuit made up of the BC 547 and its surrounding components. This section draws less than 0. 25mA. It is frequency sensitive and will not detect the 33Hz ring frequency. The other section is the "timing section, " made up of the 40106 IC. This is a hex Schmitt trigger (the same as 74C14). When a phone (that is connected to the same line as the Infinity bug) is picked up, the line voltage drops to about 12v and the whistle-detecting circuit does not see any voltage, as the 8v2 zener drops nearly all the available voltage. The transistor amplifies the signal to produce a 2v p-p signal that is turned into a DC voltage by the 10u. This turns on the latch circuit and the base of the BC 639 is raised to produce a voltage on the emitter of about 4. 5v The actual voltage on the emitter of the BC 639 is determined by the 120R in the emitter leg of a BC 547. The BC 547 is almost fully...

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