Motorola VRS750, Service Manual

Page: 35 / 104

23
Operation of VRS
Options
4
The following sections describe the operation of CPS field-
programmable options of the VRS. This includes information about
when to use an option and compatibility between options.
Base Repeater
For two-frequency simplex systems using a fixed-site repeater, you can
enable the base repeater option. This adds 300 ms of delay to the
prioritization routine to account for the fixed repeater attack time.
This allows non-priority mobiles to detect any priority mobile in the
system through the base repeater.
Mobile Detector
The Mobile Detector feature allows the user to operate VRS units with
two-frequency simplex dispatch systems without a base repeater. This
feature allows the automatic multi-unit priority resolution algorithm
to function in the above scenario. When this feature is activated by the
CPS, a non-priority VRS will send a message to the mobile to enable a
“Listen Around” feature when a proper portable PL is received.
“Listen Around” switches the mobile radio’s receive frequency to
match that of its transmit frequency of the steered mode. The non-
priority VRS will count down in priority if its corresponding mobile
does not detect the repeated transmission on the “Listen Around”
frequency. When the portable is dekeyed, the non-priority VRS will
send a second message to the mobile to disable “Listen Around” and
return to normal operation. This feature does not use any additional
user modes in the mobile.
NOTE: The Mobile Detector feature only works on
conventional modes. Trunked modes will be
unaffected.
VRS Transmit PL
Generator
The transmit PL generator, when enabled, causes the VRS to transmit
(base-to-portable), with specific field programmable PL tones. The
selected VRS transmit PL frequency cannot be the same as any of the
VRS receive PL frequencies that the portable uses to access the
vehicular repeater.
VRS Mode Steering
The VRS steering option gives the portable operator the ability to select
the current mobile radio mode via PL tones. The total number of
Mode-Steered modes can not exceed eight (including emergency,
message, and status). The operator may program as many as eight such
tones, along with corresponding mobile mode numbers, into the VRS.