With loop start interfaces, the transmitted signaling A bit in the signaling timeslot causes the interface to seize the line (go off-hook) or release the line (go on-hook).
If the A bit is set to 1, the line goes off-hook. If the A bit is set to 0, the line goes on-hook.
Bits B, C, and D are reserved, and should be set to 0.
The following illustration shows transmit signaling for loop start line interfaces:
Loop start transmit signaling
This table summarizes the transmit signaling for loop start line interfaces:
|
Bit |
Hex bitmask |
To take line off-hook |
To put line on-hook |
|
A bit |
0x08 |
0x08 |
0 |
If you reset the switch, all bits are set to 0.