Symbol CRD 1500, Руководство программиста

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1-27
AT Command Set
ERROR Otherwise
Fallback/Fall Forward: When %E2 is active, the modem monitors the line quality (EQM).
When line quality is insufficient, the modem initiates a rate re-negotiation to a lower speed
within the V.32 bis/V.32 modulation speeds. The modem continues to fall back within the
current modulation if necessary until the speed reaches 4800 bps. Below this rate, the
modem only retrains if EQM thresholds are exceeded. If the 4800 bps. EQM is sufficient for
at least one minute, the modem initiates a rate re-negotiation to a higher speed within the
current modulation speeds. Rate renegotiations are done without a retrain if a V.32 bis
connection is established.
Speeds attempted during fallback/fall forward are those available in the rate sequences
exchanged during the initial connection. Fallback/fall forward is available in error correction
and normal modes, but not in direct mode or synchronous mode with external clocks.
%L, Line Signal Level
Description
Returns a value which indicates the received signal level. This value is a comparable
indication of the receive level.
Result Codes
OK
%Q, Line Signal Quality
Description
Reports the line signal quality. Returns the higher order byte of the EQM value. Based on
the EQM value, retrain or fallback/fall forward may be initiated if enabled by %E1 or %E2.
Example
AT%Q
015
Result Codes
OK If connected
ERROR If not connected, or connected in 300 bps, V.23, or fax modes