After you transmit for a second or two then let go, you'll hear the repeater "squelch tail" - an unmodulated carrier lasting anywhere from 1 to 5 seconds. While it's transmitting you can hear if it's full quieting or some state of noise, and if your radio has an S-meter you can monitor signal strength that way too. If it's been a while since the repeater was active, it will usually issue its CW or voice ID first. Technically you've transmitted, and you need to identify while doing this. So just say your call and "testing" or "monitoring" when you do this. To trip the repeater like this is known as "kerchunking" and should be accompanied by your ID.
Mark K5LXP
Albuquerque, NM