At Commands For Testing And Debugging - ActionTec 56K PCI Pro User Manual

%B
If blacklisting is in effect, this command displays the numbers for which the last call
attempted in the past two hours failed. The ERROR result code appears in countries
that do not require blacklisting.
%Cn
Enables or disables data compression negotiation on an error corrected link.
Result Codes:

AT Commands for Testing and Debugging

The following commands are to be used for testing and debugging only and are not
meant for general use.
&&C
&&L
This command provides a loopback for line-to-line.
&&R
View Numbers in Blacklist
Enable/Disable Data Compression
Write to/Read from DSP Register
Line-to-Line Loopback
Write to/Read from DSP RAM Location
64