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 to a Public Network T1, the PBX will always be a 
slave.

The stratum clock levels define the accuracy of the clock and the 
ability to match with the incoming master clock signal.The higher 
stratum number synchronizes to the same or lower stratum 
number. For example, a Stratum 4 (PBX) clock synchronizes to 
a Stratum 3 (CO/PBX/Channel Service Unit) clock.

When the PBX is connecting to more than one T-1 signal, 
choose the order of preference of clocking sources in CDE Form Figure 18:  T1 Trunk Synchronization 
						

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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 emulate the various analog signals, (offhook, 
onhook, current reversal, etc.) and is used as the equivalent to that 
of the analog trunks.
Because A&B bits are taken from the bit stream, this signaling 
method is not appropriate for direct transmission of digital 
information unless it is modulated into an analog signal with a 
modem.
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.
Verify that the switch settings on the T1 card are set for proper 
operation. For example: 1 is closed and 2-8 are open.  
						

							Troubleshooting and Repair
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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. 
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. 
A&B bits 
Taken from each of the 24 Channels to emulate the various analog 
trunk signalling conditions (off-hook, on-hook, disconnect 
supervision, etc.) in either of the two following methods.
Superframe: Over a cycle of twelve frames, bits A&B are taken in 
frames 6 & 12 to provide basic analog trunk emulation over the T1 
facility. 
Extended superframe (ESF): ESF is not supported by the SX-200 
EL/ML or the SX-200 LIGHT. ESF is supported by an ISDN.
Refer to The S1 Switch Settings for the T1 Trunk Cable Length (not 
loop length) (page 192). 
						

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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 open
xxx1xE-lead grounded 
or open 
						

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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 call110*
Talking state110*
CO disconnects
Talking state110*
CO removes tip ground (far end hangs up)111*
PBX opens loop (idle)011*
PBX disconnects
Talking state110*
PBX opens loop (near end hangs up)010*
CO removes tip ground (idle)011* 
						

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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 text characters.
For example, to light a message waiting lamp for guest room extension 
number 2129, the customer’s PMS computer will send a string of ASCII 
keyboard commands to the PMS interface. 
The PMS message sent is: 
^BMW 1  2129^C
When the PBX’s PMS interface receives and understands the 
message, it will send an ACKnowledge character back to the 
customer’s PMS computer. 
						

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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 
12-character message, as follows:
_ _ _ _ _ _ _ _ _ _ _ _ 
function code MR
space 
status code nnnn (nnnn is a 4-byte peg count)
station number nnnnn (with trailing spaces)
PBX and PMS 5-digit Extension Number Formats
The extension number is sent between the PBX and the PMS as a 
5-digit number. Numbers that are fewer than 5 digits include spaces:
PBX to PMS extension number nnnnn with trailing spaces
PMS to PBX extension number nnnnn with leading spaces
^B
MWspace1spacespace21
29
^C
Start Trans-
action STX
The CTRL 
(^) B charac-
ter signals the 
start of a 
PMS mes-
sageEnd Tr a n s a c -
tion ETX
The CTRL (^) C 
character signals 
the end of a 
PMS messageFunction Code
The MW fol-
lowed by a space 
indicates that the 
PMS requests a 
message waiting 
functionStatus Code
1 followed by 
a space turns 
on the mes-
sage waiting 
lamp. 0 turns 
the lamp offStation’s Extension
(Room) Number
Identifies the exten-
sion number of the 
telephone on which 
the message waiting 
lamp lights. The PMS 
inserts leading 
space(s) to indicate 
that no number is 
present 
						

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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 first 10 characters of the 
name are displayed.
Replace Name^BNAM2 a-z 
XXXXX^C
Delete Name^BNAM3 a-z 
XXXXX^C
Send Message^BMW 1 
XXXXX^CInsert a space before and after the digit 1.
Delete Message^BMW 0 
XXXXX^CInsert a space before and after the digit 0.
Set Wakeup^BWKPTTTTXX
XXX^CTTTT is the time in hours:minutes. Use a 
24-hour clock. 
						

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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 Interface of the PBX
PMS problems typically occur in these areas:

PMS Protocol settings: Ensure that the communication 
parameters between the systems match.

PMS Programming: Verify that all the recommended PMS and 
Dataset programming is complete.

PMS Cabling: Use a straight-through cable between the customer’s 
PMS computer and the Dataset.
Test the PBX’s PMS interface as follows:
1. Disconnect the customer’s PMS computer from the Dataset.
2. Connect a personal computer or terminal to the Dataset’s RS-232 
port.

Ensure that the communications parameters of the personal 
computer / terminal match those expected by the PBX’s PMS 
interface.

Verify that you receive the ENQuire character from the PBX’s PMS 
interface. If not, verify that all the programming and the connections 
are correct.
3. Type the PMS message required to light a telephone’s message 
waiting lamp, using CAPITAL letters only. See the following 
example. 
						

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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 when you reconnect the customer’s PMS 
computer, check the maintenance logs for PMS related information, 
identifying problems with the customer’s PMS hardware/software. 
For the PMS to light a lamp station the Dial 0 for that tenant must be 
a console, and the Dial 0 must be the same for Night 1 and Night 2.
Faster PMS PCs may have to be forced to wait for a reply from the 
PBX.
^B
MWspace1spacexxxx
^C
Start  
Tr a n s a c -
tion STX
(CTRL B)End 
Tr a n s a c -
tion ETX
(CTRL C)Function 
CodeSta tus 
Code
1  =  ON
0 = OFFStation’s Extension
(Room) Number
Enter the telephone’s extension 
number (5 digits with leading 
spaces). 
x