Door phone call circuit
Source: InternetPublisher:拳制龙 Updated: 2013/09/24
In this doorphone circuit,an 8 ohm speaker is used both as a microphone and also an output device. The BC109C stage amplifies in common base mode, giving good voltage gain , whilst providing a low impedance input to match the speaker. Self DC bias is used allowing for variations in transistor current gain. An LM386 is used in non-inverting mode as a power amplifier to boost voltage gain and drive the 8 ohm speaker. The 10k potentiometer acts as the volume control, and overall gain may be adjusted using the 5k preset. The double pole double throw switch, reverses the loudspeaker positions, so that one is used to talk and the other to listen. Manually operating the switch (from inside the house) allows two way communication.
- Using discarded circuit boards to make small speakers
- Using ZL-680 decompression board to convert into a CD player
- Color display maintenance signal source made with integrated circuit MSE681N
- Design and production of voltage regulator for YAMAHA motorcycle
- Toshiba 2104 color TV power supply circuit
- Computer motherboard circuit diagram 815 2_27
- (Classic) Motorola L7 mobile phone schematic 7/7 (End)
- Computer motherboard circuit diagram 815 4_46
- Computer motherboard circuit diagram 820 2_30
- Computer motherboard circuit diagram 810 4_25
- Hisense Plasma TPW4218P Power Board Principle and Maintenance (Samsung V3 Screen Power Supply) - Home Appliance Repair
- Konka LC-TM2620 LCD TV black screen-Home appliance repair
- Hisense LCD TV TLM46V86PK sometimes makes strange noises when it is turned on, and the screen displays problems when it restarts - Home Appliance Repair
- Hisense LCD TV 42K431DX4F automatic shutdown fault repair example - home appliance repair
- Hisense LCD TV TLM42V78K crash repair example - home appliance repair
- Hisense TLM36H48 LCD TV has dark white raster and no image - Home Appliance Repair