US Robotics COURIER HST User'smanual page 103

COURIER HST
APPENDIX E-3
RETRAIN SEQUENCE
DESCRIPTION
E-2.4
The retrain sequence occurs at 2400 and 9600 bps. It is a
resynchronization sequence performed when one of the con-
nected modems senses that problems on the line may affect
data reliability. The procedure is essentially transparent
to users.
The following is an example of retrain events:
I. The Courier HST's receiver. sensing a need to retrain,
clamps RX to MARKs.
2. The remote modem, after receiving about 100 ms
of analog signals (a pattern of
·(f
is usually output).
clamps RX data to MARKs.
3. After the training sequence. approximately one second.
the Courier unclamps RX data and turns HS ON.
4. The remote modem reenters Data Mode.