Video data change detector

The circuit detects a change in video information and uses this to switch on an alarm in a closed-circuit television guard system or a video recorder. The circuit is usable only where the same picture is shown on the TV monitor for some time. When the picture changes, the average brightness alters and this is[…]

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infra-red controlled remote switch

Nowadays, several manufacturers produce ICs that combine an infra-red receive LED with associated amplifier and demodulator. The type SFH505A from Simens used in present circuit has, in addition, a band-pass filter to minimize any interface. It is best used in conjunction with an infrared transmitter in the next article. The output of IC1  is limited to a[…]

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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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