User's Manual

Page 5
SVR-250 Service Manual
Even though the other SVR-250s are not at priority status, they will continue to monitor the channel for
activity. If the priority unit were to leave the scene or become disabled, the other units will detect the condition
to repeat and determine that there is no priority unit repeating the transmission. They will then begin to decrement
their priority counters until one of them reaches the priority status and begins repeating the transmission. Since
the SVR-250s are all at different counts, only one will reach priority status and begin transmitting. The other
units will sense the new priority repeater and cease counting down, preserving the priority hierarchy.
If another unit were to arrive from a different scene and it is still the active priority, there will be two active
repeaters on the air when a condition to repeat exists. When one of the SVR-250s unkeys to check for handheld
activity, it will detect the presence of the other active SVR-250 and increment its priority counter and cease
transmission. This is the self clearing mode to prevent radio collisions.
ESP
TM
Priority
The SVR-250 Enhanced Sensor Priority works similar to the SVR-200 and PAC/RT formats and is completely
backward compatible with those systems. The SVR-250 determines if there is a priority (and re-establishes the
priority if missing) during idle time between conversations rather than at the critical start of a conversation. When
a condition to repeat exists, the SVR-250 is always ready.
The priority SVR-250 will transmit a short tone burst every 10 seconds. This serves 2 purposes: It informs
the handheld operator that they are still within range of the vehicle and it alerts the non-priority units that a priority
vehicle is still on scene. As long as the non-priority units hear this "beacon" every 10 seconds, they preserve their
counts and maintain the priority hierarchy. If the priority vehicle leaves the scene, after 10 seconds, the non-
priority vehicles will not hear the "beacon" and begin counting down. When one of the counts=0, that SVR-250
will send lock tone for 800 mS, assume priority and begin sending the "beacon" tone every 10 seconds as before.
Since the "beacon" tone must be heard every 10 seconds, it does not have busy carrier lock out and will send the
tone if 2 handhelds are communicating directly or in the presence of co-channel interference.
Local Mic Repeat
If the handheld operator is out of the vehicle and their partner still in the vehicle were to key the mobile radio
using the local mic, the SVR-250 will detect the local PTT and repeat the transmission to the other handhelds so
that both sides of the conversation will be heard by everyone on the link. The local mic repeat function can be
enabled/disabled via the PC software.
The SVR-250 also has a local receive audio speaker jack that enables the person in the vehicle to monitor
portable-to-base transmissions that are being repeated through the mobile.
If the users wish to communicate portable-to-portable without accessing the mobile repeater, they may
transmit on the same frequency without CTCSS (or a different CTCSS); the SVR-250 only responds to carrier
and proper tone from the handhelds.
Trunking operation
When the SVR-250 is connected to a trunking mobile and the handheld operator wishes to access the system,
they key their handheld briefly then release. The SVR-250 will attempt to acquire a voice channel on the trunking
system by keying the mobile for 800mS and monitoring the on-air detect line from the mobile. If it does not see
the radio transmit at all (system is busy), it will send a low tone to the hand held operator to alert them that the
system is busy. The SVR-250 will automatically retry every 5 seconds and send busy tone to the handheld with
each unsuccessful attempt to indicate progress of the call attempt. If unsuccessful after 30 seconds, the SVR-250
will transmit intercept tone to alert the handheld operator that the call attempt failed.