User Manual
 7000 Bus Converter User’s Manual (Version 1.8  Jan/2006, 7PH-006-18)  --------------- 56 
4. I-7551 : RS-232 to RS-232 Converter 
4.1 I-7551 Pin Assignment and Specifications: 
Introduction 
The  I-7551 Photo coupler provides a complete 
full-duplex (including control signal) electrical 
isolation channel between two RS-232 devices. 
This isolation is an important consideration if a 
system uses different power sources, has noisy 
signals or must operate at different ground 
potentials. 
The I-7551 has the option of reconfiguring which 
control signal is used. CTS can be selected 
instead of DSR and RTS instead of DTR.
The  I-7551 incorporates two  DC-to-DC 
converters; the isolation site of I-7551 is located 
in the input and output interface circuit. In other 
words, I-7551 is three- way isolation RS-232-to-
RS-232 converter.  
Specifications 
z  Input: 
 RS-232 (TxD, RxD, CTS, RTS, GND or TxD, RxD, 
DSR, DTR, GND) 
z  Output: 
RS-232 (TxD, RxD, CTS, RTS, GND or TxD, RxD, DSR, 
DTR, GND) 
z  Three-way Isolation voltage: 3000VDC 
z  Optical isolation: 2500V rms 
z Communication speed: 115.2K bps, Max 
z Distance Max: 15Meters 
z  Power requirements: +10V dc ~ +30V dc 
z  Power consumption: 1.5 W max. 
z  Storage temperature: -25℃ to +75℃ 
z Humidit
y
: 5~ 95% 










