12
LDM-MR19.2
2.1.3 A
SYNC
-
TO
-S
YNC
C
ONVERTER
The LDM-MR19.2 provides internal conversion from async to sync in compliance
with CCITT V.22 bis. According to this standard, frequency deviation between the
modem and the DTE is compensated for by shortening or lengthening the stop bit
of the async character. When the modem’s frequency is higher than the DTE’s, the
local converter extends the stop bit. When the modem’s frequency is lower than
the DTE’s, the local converter may delete one stop bit every four or eight
characters. The remote converter adds a shorter stop bit before sending the
data to the remote DTE.
For frequency deviations of up to 1.1%, the stop bits should be shortened every
eight characters (12.5%). For frequency deviations of 1.2% to 2.3%, the stop bits
should be shortened every four characters (25%).
Use switch position 2 (S2) of the “ASYNC LENGTH” DIP switch to select 25% or
12.5% frequency deviation. For proper operation of the async-to-sync converter, set
the async character length by adjusting switch positions 3 and 4 (S3 and S4) of the
“ASYNC LENGTH” DIP switch. See Table 3-3 on page 26 for detailed settings.
2.1.4 XMT L
EVEL
Four options are available for the XMT level (signal level): 0, –3, –6, or –9 dBm.
XMT level is controlled by the XMT LEVEL jumper.
