S108 - Signal Quality Selector

Description
This register affects V.32 bis, V.FC, and V.34 connections. Register S108 sets the signal quality required for the modem to handshake at the highest designated speed and for automatic rate re-negotiation. If the modem determines during carrier handshake that the signal quality is less than that specified by S108, the modem attempts to connect at the next lower speed indicated by S109, unless the N0 command is selected. If the N0 command is selected, only the speed indicated by S37 may be used (during handshake). The signal quality (such as MSE) that corresponds to each S108 value depends on line speed. That is, larger MSE values should be used at lower line speeds. The appropriate measure of signal quality may be a function of modulation and coding used. The bit error rate (BER) values that correspond to S108 values are listed below. These BER values are determined for the modem with an average channel and Gaussian noise.

Type
value

Value range
0-3, Default value: 1

Stored by &Wn
yes

Displayed by &V
yes

Values

Value   Bytes                                 

0       no limit (10-2 BER)                   

1       low quality (10-4 BER)                

2       medium quality (10-5 BER)             

3       high quality (10-6 BER)

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