At 0:19 2/10/93 -0500, Stephen D. Williams wrote:

Also, from a previous note, you wouldn't want to turn off V.42/V.42bis since that is where the error correction is. Also, even on compressed data, you get some additional bandwidth because it does packetized synchronous data. This gets close to 8bits/byte instead of 10 (start, stop).

As somebody else mentioned, you do want to turn off LAPM/V.42bis when running a speech application, because speech is a real-time application and LAPM retransmissions introduce delay. Compression is not likely to add much but delay either, since the vocoder itself is already compressing the speech much more effectively than V.42bis, which is designed specifically for textual information. Almost all modern modems support synchronous terminals, although the feature is rarely used. This is how you get around wasting 2 bits out of every 10 on start and stop bits. Phil