download manual: 7520.pdf
I-7520R
RS-232 to RS-485 Converter
For PLC user only

Input: RS-232 protocol
Output: RS-485 protocol
Speed: "Self Tuner" inside, auto switching baud rate, 300~115200 BPS
256 modules max. in one RS-485 network without repeater
2048 modules max. in one RS-485 network with repeater
Isolation voltage: 3000VDC
Repeater request: 4,000 feet or over 256 modules
Power consumption: 2.2W max.

This model is used for PLC user. The design of isolation between I-7520 and I-7520R
is different.
If the user want to supply the power from PLC, he should use the I-7520R. Otherwise
the isolation will be broken.
Please refer to the manual I-7000 bus converter for detail information