Mitel Sx 200 El/ml Technicians Handbook

Troubleshooting and Repair
81
Troubleshooting
T1 Trunk (D4 DS-1)
A T1 Trunk is a digital trunking standard that supports multiple users. 
Unlike analog trunks, the T-1 hardware signaling layer is independent 
of trunk usage; synchronization & signaling are dealt with separately.
Synchronization 
The T1 trunk establishes and maintains a connection between the 
two systems. Sampling clocks of each partner must be 
synchronized.

The Master-Slave arrangement defines the leader and follower; 
if connecting...

Technician’s Handbook
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44, T1 Network Sync (always choose a connection as close as 
possible to the defined master source clock).
Signaling Types
Channel Associated Signaling
The original idea behind the T1 is 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) stolen from the bit 
stream; used to...

Troubleshooting and Repair
83
Troubleshooting
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....

Technician’s Handbook
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Table 10:  A-B Signalling States (Tie/E&M)
PBX Port 
TypeCSU 
TypePBX port 
condition to 
channelTransmitReceiveCSU condition to 
analog facility
ABAB
Tie Trunk 
(loop start)DPO Txloop open00xxx
loop closure11xxx
DPO Rxxxx0xnormal battery
xxx1xreverse battery
DID or Tie 
Trunk 
(loop start)DPT Txnormal battery00xxx
reverse battery11xxx
DPT Rxxxx0xloop open
xxx1xloop closure
TIE Trunk 
4wire/2 
wire E&ME&M TxM-lead 
grounded or 
open00xxx
M-lead battery11xxx
E&M Rxxxx0xE-lead...

Troubleshooting and Repair
85
Troubleshooting
Table 11:  A-B Bit Signalling Example (T1/CO)
StateTransmitReceive
ABAB
Outgoing call - Basic Operation
Idle state011*
PBX grounds ring (wait for dial tone)001*
CO ground tip (dial tone applied)000*
PBX closes loop and removes ring ground110*
Dial pulsingDP10*
Completion of dialing110*
Incoming call - Basic Operation
Idle state011*
CO ground tip (interval between ringing)0101
CO ground tip (during ringing application)0100
PBX presents call0101
PBX answers...

Technician’s Handbook
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PBX Property Management
System Interface
The PBX’s Property Management System (PMS) interface collects and 
sends the following Hotel/Motel information to a customer’s PMS 
computer through a dedicated bidirectional RS-232 port – typically a 
Dataset programmed to a DNIC port.

Maid and room status 

Guest check-in and check-out 

Guest name 

Auto wake-up and message waiting 

PMS related maintenance logs.
Property Management System Messages
A PMS message is a string of ASCII...

Troubleshooting and Repair
87
Troubleshooting
The following is a PMS message format that enables a telephone’s 
message waiting lamp.
Message Formats from PBX to PMS
Maid in Room status
Maid in Room status is sent as a 10-character message, as follows:
_ _ _ _ _ _ _ _ _ _
function code STS
status code   n 
space (n is assigned room status code)
station number nnnnn (with trailing spaces)
Message Registration of Outgoing Trunk Calls
Message Registration of Outgoing Trunk Calls status is sent as a...

Technician’s Handbook
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Table 12:  PMS Keyboard Commands
CommandsPMS Keyboard 
KeysComments
Enquire (ENQ)^E^ = CTRL key
Acknowledged 
(ACK)^F
Not Acknow-
ledged (NAK)^U
Start Transaction 
(STX)^B
End Transaction 
(ETX)^C
Check In^BCHK1 
XXXXX^CXXXXX is the 5-digit extension number (use 
leading spaces).
Check Out^BCHK0 
XXXXX^C
Add Name^BNAM1 a-z 
XXXXX^Ca-z is the extension name, 20 characters in 
length (use trailing spaces), followed by a 
single space, followed by the extension 
number. Only the...

Troubleshooting and Repair
89
Troubleshooting
PBX and PMS Cannot Communicate
If the PBX’s PMS interface and the customer’s PMS computer cannot 
communicate, the system will generate PMS related maintenance log 
messages. Typically, PMS maintenance log messages will identify

Operating status of the PMS

Invalid start (STX) and end (ETX) of text message characters

Invalid function code message characters

Invalid status code message characters

Invalid room number message characters.
Testing the PMS...

Technician’s Handbook
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4. Verify that the telephone’s message waiting lamp is lit.

If the lamp is not lit, check the PMS-related logs in Maintenance. The 
logs will indicate which section of the PMS message is invalid.
5. Type the PMS message required to turn off the telephone’s 
message waiting lamp.
6. Verify that the telephone’s message waiting lamp is off.
Turning a telephone’s message waiting lamp on and off from a PC 
confirms that the PBX’s PMS interface works correctly.
If problems continue...