Switched Carrier Setting (B Modems Only); Listen Before Transmit (Lbt) Feature - GE MDS SD Series Reference Manual

MDS 05-4846A01, Rev. C
Automatic Frequency Correction (AFC) Setting
Automatic Frequency Correction (AFC), is used to counteract the slight
RF frequency drift that may occur over time or through wide swings of
ambient temperature. The default setting for AFC is
setting, proceed as follows:
1. Select
Automatic Frequency Control
spacebar to change the display to the desired setting (
2. Press the key to apply the change.
ENTER

Switched Carrier Setting (B Modems Only)

In some networks, the master unit is not keyed continuously, and trans-
mits only when it has data to send to remotes. This is known as Switched
Carrier operation, and is only for use on radios with "B" modem suf-
fixes. ("B" modems are intended for compatibility with earlier
MDS x710 radios. See "Modem Type Setting" on Page 42 for a list of
available modem types.)
Remote radios always operate in a Switched Carrier mode and should be
set accordingly.
To change the Switched Carrier setting, proceed as follows:
1. Select
Switched Carrier
change the display to the desired setting (
2. Press the key to apply the change.
ENTER

Listen Before Transmit (LBT) Feature

One challenge of operating a network with multiple data points is the
avoidance of "collisions" caused by stations transmitting at the same
time. The SD Transceiver employs a collision avoidance scheme called
Listen Before Transmit (LBT). It employs P-Persistent CSMA protocol,
which senses channel usage and inhibits transmission if the channel is
currently in use. CSMA is an abbreviation for Carrier Sense Multiple
Access.
NOTE: The Listen Before Transmit (LBT) feature requires radios to
be configured for Packet Mode operation.
LBT can be configured to behave in one of two ways; either listen on the
radio's transmit frequency (TX) or listen on the radio's receive fre-
quency (RX). Typically, Remote radios are configured to
(the default selection) to avoid collisions with the Master unit. In
SD Series Ref. Manual (Packet & Transparent Mode)
from the menu and press the
from the menu and press the spacebar to
OFF
. To change the
ON
or ).
OFF ON
, , or ).
ON AUTO
Listen on RX
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