This attribute indicates the current mode of the V.42bis decoder.
This mode can be either:
transparent - A mode of operation in which compression has been
selected but data is being transmitted in uncompressed form.
Transparent mode command sequences may be inserted into the
data stream.
compressed - A mode of operation in which data is transmitted in
codewords.
The encoder (at the mobile or Public Switched Telephone Network)
switches between the two modes depending on whether the data
coming from the Date Terminal Equipment (DTE) is suitable for
compression. The data comression function periodically determines
the compressibility of the data based on a comparison of the number
of bits required to represent a segment of the data stream before and
after compression.