Installation manual

LBI-38988
9
corrective action such as re-assigning the Control Channel to
a different operating frequency.
WORKING CHANNEL
Sub audible signaling or Low Speed Data (LSD) is
present on the Working Channel along with the primary
voice communication. The LSD indicates group call activity
on other channels and also indicates a channel drop when
appropriate.
The Working Channel operates in either the
Transmission Trunked mode or Message Trunked mode.
Transmission Trunking allows for an instantaneous channel
drop upon receipt of an "unkey" message from the mobile
radio. This is the most efficient use of channel resources.
Message Trunking provides hang time following the
channel drop message. This mode is used when it is
important to provide uninterrupted communication. When
using Message Trunking, the user(s) occupy the same
Working Channel until the message trunk timer expires..
TRUNKED FAILSOFT OPERATION
The Trunked Failsoft operating mode provides basic
trunked communications. The designated Control Channel
GETC makes all channel assignments and transmits the
assignments over the BSL (J102-3) to each of the Working
Channel GETC's. The Failsoft operating mode is entered
whenever the communications between the Site Controller
and the Control Channel GETC is lost.
Downlink
Backup
J100 J102
Trunked Site #1 of N
12 11 10 9
Rx TB10 Tx
J100 J102
Tx Rx
Audio
Repeater #1
J102 J100
GETC #1
Audio
Repeater #2
J102 J100
GETC #2
. . .
Audio
Repeater #N
J102 J100
GETC #N
Site Controller
Computer
Failsoft
Backup Serial Link
Tx Rx Tx Rx
3 4 2 5
Rx TB10 Tx
Downlink
Primary
12 11 10 9
Digital Data Path
Audio Path
.
9600 baud Modem Data
To MSC
4-Wire Audio Circuits
To MSC
3 4 2 5 3 4 2 5
Figure 1 - Typical EDACS Site Block Diagram