How do I configure the Terminal Adapter to connect at 128K (Channel Bundling)?

You must use the PPP/ML-PPP protocol to be able to bundle two channels (128K). Enable PPP/ML-PPP mode with the AT!Z=9&W0 command.

The command AT&J1&W0 is used to enable ML-PPP so that outgoing calls should be made on two B-channels. You can also bundle two B-channels (ML-PPP) for outgoing calls by using the&, !, or + characters in the dial string when seperating two numbers, (i.e. ATD384020&384030). By default, the second channel will not connect until there is high enough throughput to warrant the use of the second channel. This is called Dynamic Bandwidth Allocation (DBA).

If you don't need Dynamic Bandwidth Allocation, you can disable it with the command ATS59=0&W0. This will cause the second B-channel connection of an ML-PPP connection to be brought up immediately after the first B-channel has successfully negotiated the PPP link.

If using Windows Dial Up Networking, put this AT command string in extra settings AT!Z=9&J1S59=0&W0 or use the "MTA128ST ML-PPP" modem descriptor to allow both channels to connect immediately as opposed to waiting for high throughput before bringing up the second channel. To add the extra string, go to Start, Settings, Control Panel, Modems, Properties, Connnection, Advanced. There should be a box for extra settings.