Electronic bell-push

A solid-state bell-push is far more robust than the usual mechanical type. The touch contact may be made from an audio socket, which has a high insulation resistance and is practically indestructible. The inverting (-) input of IC1 is at half the supply voltage via R4-R5, while the non-inverting input is at earth potential via[…]

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Infra-red transmitter

Infra-red transmitter: It often happens that someone wants to watch television without the sound disturbing other people in the room. To avoid having a long cable trailing over the floor, the present transmitter (and accompanying receiver ) make it possible to listen to the TV sound wirelessly. The transmitter uses pulse-duration (=pulse-width) modulation. The modulated[…]

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Infra-red headphone receiver

Infra-red headphone receiver: This receiver is meant to complement the transmitter describe in the previous article. Its design is based on just one FET. This has the advantage that construction is simplicity ‘itself, and the disadvantage that for a sufficiently low output impedance the value of drain resistor R3 has to be fairly low. That results with[…]

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Active bass correction

Active bass correction: Active loudspeakers offer the only way of obtaining good bass reproduction from inexpensive or small enclosures. The design described does not make use, therefore, of large, heavy enclosures to obtain a good result, but of acoustic feedback. A microphone placed close to the bass drive unit unfailingly registers every movement of the loudspeaker.[…]

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