Use LM386 to make a semi-double walkie-talkie circuit

Use LM386 to make a semi-double intercom. This intercom has low cost and simple circuit. It can be used for intercom in different rooms of the office, monitoring in the baby room, etc. The calling distance can reach 2Km. 　

　working principle  　　

The circuit principle is shown in Figure 1. This circuit can only perform "half-duplex" intercom, that is, only one party can speak and the other party can listen between the host and the extension, but not both parties can listen at the same time. Listening and speaking are switched by switch S1, which is located at the host computer. The S1 position shown in the picture can be used for the extension to speak and the host to listen; if S1 is moved downward, it becomes the host to speak and the extension to listen. There is only one loudspeaker BL2 on the extension side, which serves as both a microphone and an earpiece. The same goes for the head unit speaker BL1. LM386 is used as a power amplifier. The ③ pin inputs the signal and the ⑤ pin outputs the signal. The capacitors connected to the ① and ⑧ pins can adjust the circuit gain and can be used. The power supply voltage is from 4.5-9V. The component selection and production component list is shown in the table below. No. Name Model Quantity R1 Resistor 10K 1 C1, C3 Electrolytic capacitor 10u/16V 2 C2 Electrolytic capacitor 100u/16V 1 IC power amplifier integrated circuit LM386 1 S1 switch double pole double throw 1 BL1, BL2 speaker 8Ω 0.25W 2 BL2 lead wire is best Use twisted pairs to reduce interference. If necessary, a power switch can be added to avoid power consumption when not in use. The disadvantage of this circuit is that the extension cannot call the host.