A listening method used to receive weak signals. By pressing the dedicated key to forcibly connect the receiving signal channel, the operator can distinguish the faint sound in the speaker with his ears to achieve the purpose of listening.
In order to hear the conversation of all channels, a listening method is adopted. By pressing the dedicated key, the receiving circuit receives the channel one by one in a certain order for a period of time to listen to the signal in the channel. If the receiving time of each channel is 100ms, ten channels can be scanned per second, that is, the scanning speed is 10ch/s.
3.Priority Channel Scan
During the scanning process, the set priority channel is scanned first.
4.Delete/Add Scan Channel
Delete a channel from the scan list or add it to the scan list.
When this function is activated, you do not need to press the PTT button, you can directly start the transmission operation by voice.
6.TOT: Time Out Timer
This function is used to restrict users from transmitting over time on a channel, and also to avoid damage to the walkie-talkie due to long-time transmission.
In order to save electricity and prolong the standby time, the walkie-talkie will work in a period of time off and on for a period of time without transmitting and receiving and key operation for a period of time. This method is called power saving mode. The ratio of the length of power on and off is about 1:4. When a signal is received or a button is operated, the walkie-talkie immediately exits the power saving state and enters the normal state.
This function allows users to choose high power or low power according to actual conditions.
9.Busy Channel Lockout
When using this function, users are prohibited from transmitting signals on busy channels.
The strength of the noise in the received signal corresponds to the strength of the signal. The stronger the signal, the weaker the noise. The maximum noise and the minimum noise are divided into several files, and each file is called a level. The number of divisions is called the squelch level. The user can choose according to the actual situation.
Use this function to avoid receiving irrelevant calls.
12.2-TONE/DTMF selective calling function
Use 2-TONE or DTMF signaling to select and call the corresponding walkie-talkie.
When using the frequency reversal function, the transmitting frequency and receiving frequency of the walkie-talkie will be interchanged, and the set signaling will also be interchanged.
When using the offline function, the transmitting frequency of the walkie-talkie becomes the same as the receiving frequency; the transmitting signaling is also converted to the same as the receiving signaling.
When the walkie-talkie receives a correctly coded call, it sends a signal to the caller in response to the call.
Press the dedicated alarm key, the walkie-talkie will emit an alarm sound with the loudest sound or send a predetermined alarm code to other handsets or base stations.
When the patrol personnel arrive at the patrol point, the walkie-talkie will receive the inquiry signal from the patrol register, and then automatically start the registration operation, and send its own identity code and other information to the patrol register for registration, indicating that a patrol person has arrived at the place.
Use this function to prevent misoperation of keys.
Display battery level.
It is used to operate at night or in dim conditions, and the LCD display and keys can be seen clearly.
This function allows to copy data from one walkie-talkie to other walkie-talkies of the same model.
One or several parameters of the modulation signal are used to control the change of the parameters of the carrier. According to the different control parameters, modulation can be divided into amplitude modulation, frequency modulation and phase modulation.
Refers to the sound frequency of human speech, usually refers to the frequency band of 300 Hz to 3400 Hz.
Carriers of useful signals such as voice, digital signals, and signaling, and high-frequency electromagnetic waves that are easy to transmit.
25. Channels and channel spacing
Channel refers to the frequency value occupied when transmitting and receiving. The frequency difference between adjacent channels is called channel spacing. The prescribed channel spacing includes 25KHz (wideband), 20KHz, 12.5KHz (narrowband), etc.
2-TONE, two-tone signaling, composed of two audio signals, A Tone + B Tone. Send A Tone for a period of time, and then send B Tone after a period of time. Use 2-TONE signaling to choose to call the corresponding walkie-talkie.
5-TONE, 5-tone signaling, has the same function as two-tone signaling, except that it consists of five frequencies.
CTCSS (Continuous Tone Controlled Squelch System), commonly known as sub-audio, is a technology that adds frequencies below the audio frequency (67Hz-250.3Hz) to the audio signal and transmits it together. Because of its frequency range Below standard audio, it is called sub-audio. After the interphone demodulates the received signal, the sub-audio signal is filtered and shaped, and then input to the CPU. It is compared with the CTCSS frequency set by the unit to determine whether to turn on mute. .
CDCSS (Continuous Digital Controlled Squelch System, continuous digital control squelch system, its function is the same as CTCSS, the difference is that it uses digital encoding as a condition for mute to be turned on.
DTMF (Dual Tone Multi Frequency), dual-tone multi-frequency, consists of a high-frequency group and a low-frequency group, each of which contains 4 frequencies. A high-frequency signal and a low-frequency signal are superimposed to form a combined signal, which represents a number. DTMF signaling has 16 codes. Use DTMF signaling to choose to call the corresponding walkie-talkie.