Repeater stations generally operate under automatic control. The control equipment is responsible for transmitting the repeater station's call sign at regular intervals. This identification is often done in Morse code. Some US repeater stations append a /R to end of their call sign or not (used to be required in the 80s and early 90s but no longer). Some may still have a vanity "WR#xxx" repeater license where #=0 thru 9 and xxx is any 3 letter combo but these callsigns won't be renewed and will be forced to change when their current license expires.
