Ultrashort Wave Communication Method

Ultrashort Wave Communication Method
Uses devices such as radios or walkie-talkies to conduct digital communication through voice channels. This communication method offers flexible mobility and strong real-time performance. It can track mobile carriers more quickly and continuously. It is suitable for special industries and users with existing ultrashort wave communication networks. The monitoring range is determined by the radio power and antenna installation height. In areas not yet covered by GSM, adopting the ultrashort wave communication method is practical and feasible.
Mobile Unit Product: TYTT-2000 GPS Wireless Data Modem

It uses audio modulation technology to modulate digital information into audio signals, which are transmitted to remote locations via wireless communication equipment, or demodulates digital information from audio signals received by the communication equipment. The maximum transmission distance for digital information using the TYTT-2000 depends solely on the communication equipment, and its built-in error correction coding technology ensures accurate information transmission. The TYTT-2000 features a simple external interface, easy operation and maintenance, high reliability, and wide application, such as data transmission, telemetry, remote control, target monitoring, and GPS differential positioning.
**(I) Technical Specifications
** Modulation method: MSK modulation, baud rate 2400/1200 BPS selectable
Error correction: Embedded software error correction coding ensures reliable information transmission
Audio output: 100mV RMS, 1200～2400Hz
Audio input: Input range 25～350mV RMS, input impedance 100KΩ
Operating mode: Half-duplex
Transmission mode: Automatically monitors the data interface, activates the PTT signal upon data input
Automatically distinguishes data audio from voice, with receive data muting function
Data interface: RS232C/TTL serial interface, three-wire, 4800BPS, 8-N-1 (8 data bits, no parity, 1 stop bit), XON/XOFF software flow control
Built-in 8K byte data buffer memory
Data/voice compatibility: External microphone can be connected for voice transmission, voice is automatically cut off during data transmission
Operating current: 75mA
Power supply: 8—24V DC
Rugged metal housing with anti-interference, power, receive, and transmit indicators
**(II) Usage Method
**　　The TYTT 2000 series includes two types: pure data transmission and GPS monitoring, with identical appearance and interface methods. Their respective purposes and usage methods are as follows:
**1. Pure Data Transmission Type (2100)
**　　General-purpose data transmission with no restrictions, supporting point-to-point and point-to-multipoint operation. After connecting the equipment as described below and powering on, transmission begins as soon as digital signals are input to the data port, and data is output from the data port of the receiving end.
**Communication Interface:
** GND——Signal ground, connect to the signal ground of the communication equipment.
RA——Audio signal input, connect to the audio output of the communication equipment.
TA——Audio signal output, connect to the audio input of the communication equipment.
PTT——Transmit enable signal (OC output), connect to the PTT input of the communication equipment.
MUTE——Receive data mute signal (OC output), connect to the mute input of the communication equipment.
MIC——Microphone input
**Data Interface:
** GND——Signal ground.
RD——RS232C serial data input (4800BPS, 8-N-1).
TD——RS232C serial data output (4800BPS, 8-N-1).
**2. GPS Monitoring Type (2200B, 2200A)
**　　The GPS monitoring type adds a GPS interface, alarm input, and remote control signal output on the basis of the pure data transmission type. It is divided into a master unit (2200B) and a slave unit (2200M). The slave unit can have a built-in or external GPS receiver for GPS monitoring and alarm, or it can operate without a GPS device for long-distance fixed-point alarm monitoring and switch remote control. Point-to-point and point-to-multipoint general data transmission can be performed between master and slave units; additionally, the master unit can automatically identify control data to send control information to slave units and receive GPS information and status transmitted back from slave units. (When the master unit transmits general data, the information must not contain consecutive '$GPCMD, ASCII characters)
**GPS Device Interface:
** +5V——+5V DC output, maximum current 300mA
GND——Common ground
GPS-RXD——NMEA 0183 format data input (4800BPS 8-N-1), connect to the data output of the GPS device
GPS-TXD——Connect to the data input of the GPS device for receiving RTCM differential signals
The following are the control information input and return information output protocols of the master unit (input and output via the data port)
**(1) Control Information
**$GPCMD,XXXX,XX,XXX,XXX,XX
① 　 ② 　 ③  ④  ⑤  ⑥  ⑦
① Information start character;
② Called target address code; when calling a group continuously, it is the first address of the group;
③ Number of times the target returns information;
④ Time interval for the target to return information; when monitoring, it is the monitoring time (in "seconds");
⑤ Number of targets called continuously;
⑥ Control flag:
　　00 Normal call
　　11 Turn on master control switch
　　22 Turn off master control switch
　　33 Turn on slave control switch
　　44 Turn off slave control switch
　　55 Monitor target audio
⑦ Information end character (carriage return, line feed).
**(2) Return Information
**$GPRMC, Target code Latitude Longitude Speed Direction angle Status
① 　　② 　③  　④ 　⑤  　⑥　  ⑦ 　⑧
① Information start character;
② Called target address code (4 bytes);
③ Target location latitude ddmm.mmm (7 bytes, decimal point not transmitted);
④ Target location longitude dddmm.mmm (8 bytes, decimal point not transmitted);
⑤ Target movement speed 000-999 (3 bytes, unit: "knots");
⑥ Target movement direction 00-36 (2 bytes, unit: "10 degrees");
⑦ Status flag;
　　00 Normal
　　88 Alarm status 1
　　99 Alarm status 2
⑧ Information end character (carriage return, line feed).
When no GPS device is connected or the GPS device has not achieved positioning, the information in ③ ④ ⑤ ⑥ is replaced by ":".