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Password electronic doorbell 1

2014-11-07 14:26  
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Password electronic doorbell 1
The password electronic doorbell circuit is composed of the electronic password circuit and music occurred circuit, and it is shown in Figure 3-118. Electronic password circuit consists of integrated circuits lCl and keys Sl-S6, diodes VDl-VD5. lCl is the electronic password IC, its pin 1-3 and pin 6 are the effective transmission input ends, and pin 7 is the reset end, when the pin 1, 2, 3, 6 are input high trigger level in turn, only pin 5 outputs high. Otherwise, pin 5 is in low level. R uses the 1/4W carbon or metal film resistor. VDl-VD5 select the 1N4148 silicon switch diodes.