Service manual

OPERATION
3-23
April 2001
Part No. 001-9800-203
with the same system number, system information is
loaded only once. Therefore, there is no delay with to
change systems which results in very efficient scan-
ning of those positions. The group select and group
scan functions are not available with this transceiver.
3.7.7 SCANNING CONVENTIONAL SYSTEMS
As described in Section 3.4.7, conventional
systems select blocks of up to sixteen channels, and
groups select a channel within that block. With the low
tier models, each display number programmed for
conventional operation selects a specific radio
channel, and channels are scanned in system sequence
(see preceding section). With high tier models, group
scanning determines whether calls are received on all
channels (groups) or only the last selected channel of
selected or scanned systems.
With all models, Call Guard squelch is detected if
the monitor mode is disabled (see Section 3.9.1). If the
monitor mode is enabled, all calls occurring on a
channel (group) are received. Priority group sampling
is also available with scanning. Refer to Section 3.9.6
for more information.
A feature called Adaptive Tone Scan (ATS) is
used when scanning conventional channels. If no
carrier is detected, the channel is scanned for only 40
ms. If a carrier is detected, searching for Call Guard
signaling occurs (if programmed). If the tone type of
Call Guard squelch is programmed, the channel is
monitored for 180-420 ms. The shorter time is when
the tone is outside certain limits, and the longer time is
if it is at or near the programmed value. If digital type
is programmed, approximately 350 ms is required to
determine an invalid code (less time is usually
required to detect valid codes).
3.8 LTR FEATURES
3.8.1 SYSTEMS
When a system is programmed for LTR opera-
tion, information such as repeater channel numbers,
home repeater, and all encode and decode ID codes are
specified. The ID codes can be fixed, selectable, and
block types. The types of ID codes and the number
that can be programmed in each category are shown in
the following table. Any combination of codes can be
programmed and all codes can be different.
3.8.2 GROUPS
NOTE: Receive-only LTR groups are programmed by
an encode ID of β€œ0”.
The group select function chooses the selectable
encode and decode ID codes (high tier only). Only the
selected encode ID code is sent when transmitting (it
is not possible to place a call to more than one code).
Calls are received on the selected ID code plus any
fixed priority and block decode codes. The group scan
feature (high tier only) determines if calls are received
on all or only the selected ID code of a selected or
scanned system.
As previously stated, low tier models can be
programmed with up to sixteen system/group combi-
nations. In addition, the group select (and therefore
group scan) features are not available. Refer to Section
3.7 for more information.
3.8.3 RECEIVE PRIORITY ID CODES
General
With standard (dispatch) calls, the fixed, select-
able, and block ID codes have a priority order so that
an incoming call with a higher priority ID code can
interrupt a lower priority call in progress. Conven-
tional systems can have another type of priority which
is described in Section 3.9.6.
One use of receive priority is to allow someone
such as a dispatcher to interrupt calls in progress with
an important β€œall call” message. If the transceiver
detects a call with a higher priority ID than the one it
is receiving, it immediately drops the current call and
switches to another repeater to receive the higher
priority call. Telephone calls are not interrupted by
Decode (Receive) Encode (Transmit)
Fixed
2N/A
Selectable
1 (low tier) 1 (low tier)
16 (high tier) 16 (high tier)
Block
Up to all 250 N/A