Light controlled ringing circuit diagram

Ordinary telephone ringing circuits are mostly composed of KA2401 and peripheral components. When installing a light- controlled bell, you only need to connect the light-controlled circuit shown in country (b) at the "X" in country (a): the external line has When the AC ringing signal is input, pin 8 of KA2401 outputs a two-tone ringing signal. If it is daytime, the resistance of the photosensitive tube 3DU is small, the thyristor SCR is turned on, and the ringing sound is loud; if there is no light at night, the resistance of 3DU is very ( Several megohms), the ringing signal can only pass through R2 after being attenuated, and the ringing sound will be much smaller.
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