Description: aluExtDS1SignalBitsState is an array of bytes used to indicate the
current state of the ABCD signalling bits for all timeslots of a
DS1/E1.

The first half of the array or the 32 most significant bytes describe
the RX ABCD bits. The other half describes the TX ABCD bits.

In each half of the array, every byte represents a particular timeslot.
The most significant byte represents timeslot 1. The least significant
byte represents timeslot 32.

The byte arrangement is as follows:

array index: |  0  1 ... 30 31 | 32 33 ... 62 63 |
timeslot:    |  1  2 ... 31 32 |  1  2 ... 31 32 |
             | <---- RX -----> | <---- TX -----> |

Each byte carries ABCD bits in the least significant nibble. The
byte's most significant bit indicates the validity of the ABCD bits.

The bit arrangement is as follows:

bit pos:    | 7 6 5 4 3 2 1 0 |
            | V x x x A B C D |

'V' - validity (0 = invalid, 1 = valid)
'x' - don't care

ABCD bits are marked invalid for a variety of situations (eg.
tmnxDS1SignalMode not configured for CAS, timeslot(s) not configured
as part of a channel-group, DS1/E1 status not up, etc.).

For CAS DS1 SF, only the AB signalling bits are supported. The remaining
2 least significant bits in the nibble are undefined.