- Sep 06, 2017 -
The walkie-talkie is a two-way mobile communication tool, composed of transmitting part, receiving part, modulation signal and modulation circuit, signaling processing and so on. In the case of no need for any network support, you can call, no calls generated for relatively fixed and frequent calls occasions. Walkie-talkie There are analog walkie-talkie, digital walkie-talkie, IP walkie-talkie and other three categories.
The walkie-talkie can be used for contact and command scheduling among group members to improve communication efficiency and improve the ability to respond quickly to emergencies. There are also some special occasions to use the walkie-talkie, such as explosion-proof walkie-talkie, waterproof walkie-talkie, police walkie-talkie and so on. Car station can also be included in the use of radio.
The working principle of the walkie-talkie is as follows:
1, the launch part:
Phase-locked loop and voltage-controlled oscillator (VCO) to generate the radio frequency carrier signal, through the buffer amplification, excitation amplification, power amplifier, resulting in rated RF power, through the antenna low-pass filter to suppress the harmonic components, and then launched through the antenna The
2, the receiving part:
The receiving section 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 and generates a first intermediate frequency signal. The first intermediate frequency signal further eliminates the adjacent channel clutter signal through the crystal filter. The filtered first intermediate frequency signal enters the intermediate frequency processing chip, and then mixes with the second localized signal to generate the second intermediate frequency signal. The second intermediate frequency signal is filtered out by a ceramic filter and then amplified and discriminated, Generate an audio signal. Audio signal through the amplification, band-pass filter, de-emphasis and other circuits, into the volume control circuit and power amplifier amplification, drive the speaker, get the information people need.
3, modulation signal and modulation circuit:
The voice of a person is converted into audio by a microphone
4, signaling processing:
CPU generates CTCSS / CDCSS signal through the amplification adjustment, into the voltage-controlled oscillator for modulation. The low frequency signal obtained after receiving the frequency discrimination is filtered and shaped by the band-pass filter of the amplified and sub-audio, and the CPU is compared with the preset value to control the output of the audio amplifier and the speaker. That is, if the same as the preset value, then open the speaker, if different, turn off the speaker.
1. Walkie-talkie without network restrictions, the network is not covered to the place, walkie-talkie allows users to easily communicate
2. The walkie-talkie provides one-to-one, one-to-many calls, one click and say that the operation is simple, so that communication is more free, especially in the case of emergency scheduling and collective collaboration, these characteristics are very important. 3. Low call costs
The walkie-talkie is mainly used in the fields of public security, civil aviation, transportation, water conservancy, railway, manufacturing, construction and service. It is used for communication and command and dispatch of group members to improve communication efficiency and improve the ability to deal with emergencies. With the walkie-talkie into the civilian market, people travel, shopping began to use more and more walkie-talkie.
There are also some special occasions to use the walkie-talkie, such as explosion-proof walkie-talkie, waterproof walkie-talkie, police walkie-talkie and so on. Car station can also be included in the use of radio.
Access control intercom
With the progress of science and technology, walkie-talkie in the security industry more and more widely used, access control intercom system is the case. Access control intercom is the application of the walkie-talkie in the access control system, the user through the walkie-talkie to talk or video communications, access control intercom system mainly by the intercom host, intercom extension, UPS power supply, electric lock and door closers and other components. According to the type can be divided into straight, digital, digital households through, direct-style video intercom, digital video intercom, digital households through visual intercom and so on.