Isolated RS-232 to RS-232 Converter

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 provides 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 the I-7551 is located in the input and output interface circuit. In other words, the I-7551 is 3-way isolation RS-232 to RS-232 repeater.



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    • 3000 VDC 3-way Isolation Protection
    • ESD Protection
    • Power Input, +10 ~ +30 VDC
    • Baud Rate, 300 ~ 115200 bps
    • Operating Temperatures, -25 °C ~ +75 °C
    • DIN-Rail


    Hardware Specifications

    Input TxD, RxD, CTS, RTS, GND or TxD, RxD, DSR, DTR, GND
    Jumpers JP1 and JP2 are used to select the RS-232 input source type
    Output TxD, RxD, CTS, RTS, GND or TxD, RxD, DSR, DTR, GND
    Transfer Distance Max. 15 M at 115200 bps
    Speed 300 ~ 115200 bps
    ESD Protection Yes
    3000 VDC Three Way Isolated Protection Yes
    Connection RS-232 Input 9-Pin Female D-Sub
    RS-232 Output 9-Pin Male D-Sub
    LED Indicators
    Power/Communication Yes
    Input Voltage Range +10 VDC ~ +30 VDC (Non-isolated)
    Power Consumption 1.2 W
    Casing Plastic
    Flammability Fire Retardant Materials (UL94-V0 Level)
    Dimensions (W x H x D) 72 mm x 118 mm x 35 mm
    Installation DIN-Rail
    Operating Temperature -25 °C ~ +75 °C
    Storage Temperature -30 °C ~ +75 °C
    Humidity 10 ~ 90% RH, non-condensing

    Hardware Structure


    Internal I/O Structure



    Ordering Informations

    I-7551 CR Isolated RS-232 to RS-232 Converter (RoHS)
    I-7551-G CR Isolated RS-232 to RS-232 Converter (Gray Cover) (RoHS)



    7520-Series User Manual