Typically on LTR systems, each of these controllers periodically sends out a data burst (approximately every 10 seconds on LTR Standard systems) so that the subscriber units know that the system is there. The idle data burst can be turned off if desired by the system operator.
On LTR systems, usually, each controller periodically broadcasts a data signal (approximately every 10 seconds on LTR Standard systems) to indicate the system's availability. The idle data signal can be deactivated by the system administrator.