S7-200 question

Hi all,

I am using a S7-200 226 PLC with a CP243-1 Ethernet module connected to a wireless radio. on the other side is a S7-300 314C-2DP PLC with a 343-1 lean which is connected to a wireless radio.
My question is, is there a way to tell when the S7-200 looses communication if the wireless signal drops. I Need to have an alarm light come on when this would happen on the S7-200 side.

Thank you

Send over a heartbeat bit from the 300 to the 200 and use the cycling heartbeat to detect if comms has failed.

How do you go about making a "heartbeat" bit and cycling heartbeat?