It defines the number of repeats as a local variable and the incoming- and outgoing topic for the rfx-devices. At first entry the rfx-topic is changed to the desired rfx-topic and the output is fired. The node outputs the signal to the rfx-device and it is also fed into a delay-node (in this example 500ms). Then the messages is forwarded into the function again, where it detects that the topic does not equal the initial topic so it just increases the iteration number and fires the msg again. This is repeated until the msg.iteration is larger than the repeat variable. Then the loop ends.
I would trigger the input with a crontab node, as the trigger needs to be fired at fixed point in time.
Not sure if this is the best and most safe solution, but it works for me.