Free electronic circuit design and schematic diagram
Door intercom is very useful for home security. If you receive a door knock or door bell/alarm, you can push this intercom knob and ask the guest to identify his/her self, before deciding to open the door to welcome. Here is the schematic diagram of the circuit: To install this door intercom, except for right side speaker, you should place […]
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Below is a 2-station intercom using common 8R mini speakers. The “press-to-talk” switches should have a spring-return so the intercom can never be left ON. Power the speaker from a separate power supply is the secret to preventing instability (motor-boating) with a high gain circuit like this. An extra station (or two extra stations ) can be connected to this […]
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