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2 Transistor FM Voice Transmitter... [read more]

A simple circuit, peak indicator of tops of musical signal. Each time where the level of signal exceeds the level + 4dB, turns on led D1. It is useful in each channel of console of sound, in final amplifiers or in that other application, to we needed. With the prices of circuit, the indicate begins with levels above + 4 dB (1.25V rms). For adaptation in different levels of signal, we can use a trimmer, before capacitor C1.... [read more]

This circuit could be used for replacing your manual volume control in a stereo amplifier. In this circuit, push-to-on switch SW1 controls the forward (volume increase) operation of both channels while a similar switch SW2 controls reverse (volume decrease) operation of both channels. A readily available IC from Dallas semiconductor, DS1669 is used here.... [read more]

A time delay relay is a relay that stays on for a certain amount of time once activated. This time delay relay is made up of a simple adjustable timer circuit which controls the actual relay. The time is adjustable from 0 to about 20 seconds with the parts specified. The current capacity of the circuit is only limited by what kind of relay you decide to use.... [read more]

The LM317T output current can be increased by using an additional power transistor to share a portion of the total current. The amount of current sharing is established with a resistor placed in series with the 317 input and a resistor placed in series with the emitter of the pass transistor.... [read more]

This circuit is intended to let the user turn off a lamp by means of a switch placed far from bed, allowing him enough time to lie down before the lamp really switches off.... [read more]