Binary logarithmic ladder network

Binary logarithmic ladder network: The network provides an attenuation between 0 dB and 78.75 dB that is presettable in 64 steps with the aid of a 6-bit code. Six independent, relay switched attenuator sections may be connected in series in accordance with the input code. Since the sections have identical 1 kΩ impedances, they do[…]

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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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