14
LDM-MR19.2
However, there is a difference in multipoint applications, where the master
modem communicates with modems at different distances. When the master
modem is set to AGC-ON, the master can communicate across long distances (up
to its maximum range) to the slave modems. However, this setting increases the
RTS-to-CTS delay. For example, under AGC-ON, the CTS delay of all slaves must
be set to 64 ms when the data rate is less than 9.6 Kbps.
When the master modem is set to AGC-CNTR, it can’t transmit or receive across
as much distance. However, the polling goes faster. For example, under AGC-
CNTR, the CTS delay of all units can be set to 8 ms when the data rate is greater
than or equal to 4.8 Kbps.
Table 2-1, below, contains general guidelines for choosing AGC and CTS-delay
settings. Each application is unique, however; you might find that your LDM-
MR19.2 system works better when the units are set slightly differently.
Table 2-1. Recommended Multipoint AGC and CTS-Delay Settings
Distance
Data Rate
Master
Master
Slave
Slave
Between
AGC
CTS Delay
AGC
CTS Delay
Modems*
Short range
≤
2.4 Kbps
CNTR
64 ms
CNTR
64 ms
Short range
>2.4 Kbps,
CNTR
8 or 64 ms
ON
64 ms
<4.8 Kbps
Short range
≥
4.8 Kbps
CNTR
8 or 64 ms
ON
8 or 64 ms
Long range
<9.6 Kbps
ON
8 or 64 ms
ON
64 ms
Long range
≥
9.6 Kbps
ON
8 or 64 ms
ON
8 or 64 ms
* “Short range” = up to 2.8 mi. (4.5 km) for data rates of 9.6 or 19.2 Kbps or up to 3.7 mi. (6 km)
for data rates of 3.6 to 7.2 Kbps. “Long range” represents distances greater than these.
