The functions of the walkie-talkie buttons:

(1) The rotary switch in the middle is the channel selection switch.

(2) The knob switch on the right is the power switch/volume controller knob.

(3) The big button on the left side, PPT switch, press and speak into the microphone to call the other party, release to receive.

(4) The two small keys in the middle and below on the left side are used to define various functions, which are defined through frequency writing software.

Extended information

The working principle of the walkie-talkie is as follows:

1. Transmitting part:

Phase-locked loop and voltage-controlled oscillator ( VCO) generates a transmitted RF carrier signal, which is buffered, amplified, exciter amplified, and powered to generate rated RF power. It passes through the antenna low-pass filter to suppress harmonic components, and then is emitted through the antenna.

2. Receiving part:

The receiving part mixes the amplified signal from the radio frequency with the first local oscillator signal from the phase-locked loop frequency synthesizer circuit at the first mixer frequency and generates the first intermediate frequency signal. The first IF signal passes through a crystal filter to further eliminate clutter signals in adjacent channels. The filtered first IF signal enters the IF processing chip and is mixed again with the second local oscillator signal to generate a second IF signal. The second IF signal passes through a ceramic filter to filter out unwanted spurious signals, and then is amplified and frequency-identified. Generate audio signals. The audio signal passes through amplification, bandpass filter, de-emphasis and other circuits, enters the volume control circuit and power amplifier for amplification, drives the speaker, and obtains the information required by people.

3. Modulation signal and modulation circuit:

Human voice is converted into audio electrical signal through the microphone

4. Signaling processing:

The CTCSS/CDCSS signal generated by the CPU is amplified and adjusted, and then enters the voltage controlled oscillator for modulation. After receiving the low-frequency signal obtained after frequency identification, part of it is filtered and shaped by amplification and sub-audio bandpass filters, enters the CPU, and is compared with the preset value, and the result controls the output of the audio amplifier and speaker. That is, if it is the same as the preset value, the speaker will be turned on, if it is different, the speaker will be turned off.

Reference: Baidu Encyclopedia: Walkie-Talkie