a. Receive GSM short message without PDU code, output By ASCII code, Chinese character GB code form through standard RS232 interface.  Com baud rate: 9600bits/s.
b. Amount of message: 70 Chinese characters each message
c. DB9 Com:  2 PIN output, 3 PIN input, 5 PIN GND.
d. Power supply: voltage: DC 4.5V — 5.5V,, max current:300mA
e. Shield non-privileged message. Use identify code or verify code to judge if the message is acceptable.
f. Feedback
Within 2 seconds after receipt the information from receiving DTU, the control card of the LED display or the computer will give a feedback to GSM DTU, then GSM DTU send the
feedback to the sending terminal by SMS. In such way, users can know the receipt situation of each terminal real-time.

Technical parameter:
Processor and memorizer: 8 bits low power consumption proccesor, 
Frenquency: 900MHZ, 1800MHZ, 1900MHZ
Power supply Voltage:DC 5V/500mA, working current:250mA,
idle current:<65mA
Antenna impedence:  50Ω/SMA
Receiving sensitive: -104dbm
SIM  card: 3V/5V, test automatically
Interface:  RS232 (DB9), Baud rate:1200~57, 600bits/s
Dimension: 92.7x61.3x23mm
Weight: 300g
Working temperatur:-30?C~60
humidity: 0-95%