Technical information

Technician’s Handbook
86
Table 10: A-B Signalling States (Tie/E&M)
PBX Port
Type
CSU
Type
PBX port condi-
tion to channel
Transmit Receive
CSU condition to
analog facility
A B A B
Tie Trunk
(loop start)
DPO Tx
loop open 0 0 x x x
loop closure 1 1 x x x
DPO Rx
x x x 0 x normal battery
x x x 1 x reverse battery
DID or Tie
Trunk
(loop start)
DPT Tx
normal battery 0 0 x x x
reverse battery 1 1 x x x
DPT Rx
x x x 0 x loop open
x x x 1 x loop closure
TIE Trunk
4wire/2
wire E&M
E&M Tx
M-lead
grounded or
open
0 0 x x x
M-lead battery 1 1 x x x
E&M Rx
x x x 0 x E-lead open
x x x 1 x
E-lead grounded
or open