Lucent Technologies SLC ConnectReach User & Service Manual page 305

Installation
Analog Voice Interface Considerations
FXS (Continued)
T1 state transitions
In some cases, invalid T1 state transitions are ignored.
Using ESF
When using ESF, the SLC ConnectReach system ignores all transitions where the
A and C bits have different values. (For example, a transition from 1010 to 1000
will be ignored.)
E&M trunks
On E&M trunks, the SLC ConnectReach system ignores the B (and for ESF, the
D) bits. (For example, a transition from 1111 to 1010 will be ignored on an E&M
trunk.)
Can never happen
Some state transitions that can never happen are ignored. [For example, on
loop- or ground-start trunks, a transition from 0000 (ringing) to 0100 (current feed
reversal) is ignored, since ringing only occurs on incoming calls, and current feed
reversal only occurs after an outgoing call is answered.]
363-208-050
Issue 4 June 2002 5-53