An ''alarm only [JSup tag|tag]'' can only be used for its [JSup tag alarms|alarm] by the [JSup Alarm system|alarm system].

An ''alarm only [JSup tag|tag]'':
 * Has to be [JSup Read only tags|read only] also.
 * Must have a single ''read-only'' [IOHook|I/O hook].

No [JSup Code|code] or [JSup Animations|animation] can read or write the value of an ''alarm only [JSup tag|tag]''.

The advantage of using ''alarm only [JSup tag|tags]'' is their low cost for [JSup licence|licence] I/O tag count.
Indeed an ''alarm only [JSup tag|tag]'' count only an 1/8th of an I/O tag for [JSup licence|licence] limitation. 
So an alarm collecting/recording [JSup application] would be very cheap, because every 8 ''alarm only [JSup tag|tags]'' only one I/O tag is counted for [JSup licence|licence] I/O limitation.