Mitel SX-200 ICP - 1.0 5020, Руководство техника

Страница: 235 / 360

227
Basic Troubleshooting and Repair
Signaling Types
Channel Associated Signaling
T1 was originally designed to emulate 24 independent analog trunks. The
Channel Associated signaling supports Loop Start, Ground Start, DID/
Loop, and E&M trunks. The function of each channel is decided and
programmed at each end.
All handshake signaling is done with bits (A&B) taken from the bit stream
which are used to emulate the various analog trunk signals, (off-hook,
on-hook, current reversal, etc.).
Common Channel Signaling
The Handshake signaling for the first 23 channels is managed by the 24th
channel. The Common Channel signaling allows for transmission of digital
information and more advanced digital trunk applications (MITEL’s MSDN,
Bell Canada’s Megalink, ISDN, etc.). Signaling protocol is defined by the
type of service.
Test/Verify (T1)
Synchronization
Most T1 issues are a result of connectivity problems. Verify that the
incoming T1 signal is seen at both ends; verify all hardware connections.
Failure at either end indicates loss of an incoming synchronizing signal.
Loopback
Loopback is used to verify and locate the source of either a cable or a
synchronization problem through the devices in a T1 transmission path.
Devices in the T1 transmission path (PBX, CSU, Channel bank, smart
jacks, etc.) will generally have some type of loopback mode. Loopback
modes will typically have the effect of taking the input T1 stream and
transmitting the stream back to the source; the nodes thereby verify that
portion of the link.
In the absence of a loopback mode, the T1 transmits and receives pairs
that can be directly connected together to physically create a loopback
condition.