UPS PLC notification using PLC input terminal

[Didro 0]

Hello All ! We use FX3U PLC and our customer wants to use UPS. When power supplier is down, PLC should sent message by GSM-modem. We plan to use simple APC Back-UPS (320VA). But our PLC has only one RS-232 port, and we already use it. Could we somehow connect UPS to PLC direct by PLC's input terminal? Thank you

[Crossbow 296]

Most industrial grade UPS units have a relay output which indicates when running on UPS power. I used a Mitsubishi UPS on a project years ago. I took the relay output and wired the relay contacts to turn on a PLC input to indicate it was on UPS power. If it doesn't have a relay, and you're not able to use the RS232, what way would you expect it to indicate to the PLC it was on? Only thing I can come up with is wire a relay to the output of the UPS and one to utility power, and then look for the UPS one to be on and the utility power one to be off.