Comdial Dxp Plus Instructions Manual

							1.1 Introducing The DXPT1
The DXPT1 is a digital interface board supporting up to 24 simultaneous calls on two pairs of wire. The
advantages of T1 over single-channel systems are largely:
·Cost savings (much lower price per channel)
·Greater reliability
·Uses less copper wires
·Improved voice reproduction
·More features available
T1 is over 20 years old but the services have been upgraded during this time (for example, extended
superframe).
T1 uses time division multiplexing techniques which multiplexes 24 channels in a stream. Each channel
is 8 bits wide.  The total is 24 channels x 8 bits = 192 bits for user information. An additional bit is added
at the beginning of the stream to identify the particular frame. A frame every 125 msec or 8000/second.
12 frames make up a superframe for standard T1. ESF mode requires 24 frames per superframe. The
frame bit in superframe mode is used 100% of the time. The sequence for the frame bits is:
100011011100. The first bit of each frame (frame bit) repeats over and over
||
A B Of the 12 frames, the 6th and 12th contain the “A” and “B” signalling bits respectively.
The signalling is inband (mixed with the channel). For the two binary bits (A and B), only four combina-
tions are possible (00, 01, 10, 11). These bits are assigned according to the signalling protocol (for
example, E&M, DID, Loop Start, and Ground Start). See section 3, “Troubleshooting The Protocol
Layer.”
The span speed is 1.544 MHz (193 x 8000/sec).
For extended superframe (ESF), the frame-related bits in the 24 frames are:
ESF Framing Format
mcm0mcm0mcm1mcm0mcm1mcm1...6 frame bits (0 or 1) on frames 4, 8, 12, 16, 20, 24 (2 Kbps)
12 maintenance bits  (m) (4 Kbps)
6 CRC error checking bits (c), if enabled (2 Kbps)
Therefore, all of the 24 non-user bits (frame, maintenance, and error checking) use a bandwidth of 8 Kbps
out of the total bandwidth of 1.544 Mbps.
The A and B signalling bits are inserted over the least significant bits (LSB) of each channel in the 6th
and 12th frame respectively. This does not change the speech encoding enough to be detected by the user.
The A and B signalling bits are repeated in the 18th and 24th frames.
1.2 Describing The Channel Service Unit (CSU)
The DXPT1 board has a CSU built into the board. This allows direct connection to the network (DS1
level). If a CSU was not built-in, the connection would be DSX-1 and would only transmit 655 feet to the
nearest 66-type connector block. The CSU increases signal drive to 1 mile, provides electrical isolation
(1500 volts), and provides automatic line build out (ALBO). The output is set depending on the received
signal level strength. When a strong signal is received, the transmit level is -15 dB. When a weak signal is
received, the transmit level is 0 dB. This ability to adjust output levels prevents over driving a line
repeater in the network, if directly connected. If a customer still wants to add an external CSU, he/she
may do so. Normally, the DXPT1 is connected to a central office “smart” jack. The customer’s savings
from using the built-in CSU can easily amount to approximately one thousand dollars, at today’s prices.
NOTE: If an external CSU is added by the installer for the purposes described above, and the mode is
Extended Superframe, check the SW2-2 switch for the correct ID, if in conflict.
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							1.3 Considering Pre-Installation Details
CAUTION
For operation with the DXP Plus, the T1 board must be Revision B or higher. If the T1 board that you
are installing is a lower revision, contact Comdial Technical Services (1–800–366–8224) for advice
before you proceed with the installation..
If you are the installer, you must consider the following things to ensure a proper installation.
A. Determine the T1 trunk configuration and communicate this to the central office and/or the network
for coordination and assignment of service.
B. Determine whether the dial type is tone or pulse.
C. If DID or E&M protocols are going to be used, determine the number of DTMF receivers needed.
D. If the above protocols are used, coordinate the blocks of numbers assigned with the data base.
E. For DID and E & M protocols, determine the type. Wink start, delay dial, or immediate start are
available. Wink start is very popular. If you choose immediate start inbound, select dial pulse over
tone dial to ensure that the DXP has enough time to react.
F. AT&T will not supply dial tone unless the customer ordered this feature. However, if you enable the
automatic route selection (ARS) feature, it will supply dial tone.
G. Configure an interface cable (8-conductor cable terminated with modular jacks) to connect to the
DXPT1. See section 4 inInstalling  The DXPT1 Digital Carrier Transmission Option,IMI89–193 for
more instructions. Pins 7 and 8 must be open at the DXPPlusend for DXPT1 Issue 2 while Issue 3
boards and above will not require pins 7 and 8 to be open. A smart-jack often connects pins 7 and 8 to
chassis ground. If the chassis ground is connected at the smart-jack, the DXPPlusreceive will most
likely show loss of signal. (Pins 1 and 2 are shorted to 7 and 8 to allow for an inverted cable to be
used.)
H. Order spare boards, if needed.
I. Make sure you have a synchronization card to install on the auxiliary board.
J. Determine the optimum DXPT1 board configuration. If a T1 board occupies a universal slot, more
stations are possible than by using analog trunk boards.
K. If fractional T1 is being considered, decide whether 8-, 16-, or 24-channel mode is most beneficial.
L. Verify that primary lightning protection (such as gas discharge tubes) is provided where the T1
copper wires enter the building. This should be the case when a smart jack is installed by the central
office.Primary protection is a must since the DXPT1 contains only secondary protection.
M. For a DXP-to-DXP application, where no outside network exists, only one synchronization card is
required. The designated “master” DXPPlusdoes not require a synchronization card.
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							2 Troubleshooting The Physical Layer
SW1, SW2, and the LIU switches must be set up according to the customer’s requirements. SeeInstalling
The DXPT1 Digital Carrier Transmission Option,IMI89–193 for directions.
2.1 Selecting Functions With DIP Switches SW1-1 Through SW1-8
NOTE: SW1 switch contents will be updated only during a reset operation.
The mode, superframe or extended superframe, is critical. If set wrong, the board will not find frame sync
causing the red Sync LED to light.
Yellow alarm mode (SW1-4) is always off, unless the customer is in Japan.
Suppression is defaulted to B7. If digital data is ever presented to the DXPT1 board from a drop and
insert multiplexer (mux), or any other means, B8ZS will be required even though the channel is disabled
in the DXPPlus. The digital data could be all zeros violating the ones density requirement of 1 in 8 bits in
a channel. The network or mux must also have B8ZS enabled. If B8ZS is being sent in any channel the
green LED above SW1 will flicker if SW2-6 is enabled. Do not set SW1-5 and SW1-6 to the “no
suppression” setting unless approved by Comdial Engineering. The “no suppression” setting is for
possible future needs.
SW1-7 and 8 are critical to the channel capacity required.
2.2 Selecting Functions With DIP Switches SW2-1 Through SW2-8
SW2-1 is valid only in the superframe mode. This switch must be “on” if the network is capable of
initiating an inband loopback. The switch will not cause a remote loopback but it will look for the
command from the network. Leaving the switch “on” does not hurt anything whether the network can
perform the loopback operation or not. A reset is not required when changing the switch.
SW2-2 is programmed at reset in the ESF mode only, and it will always be “off” (default) unless the
network requires the facility data link messages to be a different ID. The default is customer premise
equipment. If the network requests that the messages have a carrier-type header ID, turn the switch “on”
and reset the board. This will probably never need to be “on”.
SW2-4 is for reporting CRC errors in the ESF mode, if the network has the ability to support the CRC
feature. The default position is “off” to prevent false errors when the error checking is not supported by
the network.
SW2-5 is to allow or prevent the sending of facility data link message packets in ESF mode during a
preemptive yellow alarm and loopback messages. The ANSI specification allows FDL packets to be
stopped during a yellow alarm and loopback, but some customers/networks want the packets to continue.
Switch changes require a reset to be programmed.
SW2-6 defines the meaning of the green LED labeled “B8ZS/COFA.” A reset is not required when
changing this switch. When the switch is “off” (default), the LED indicates COFA detected. When the
switch is “on,” the LED indicates B8ZS detected. B8ZS detection is handy to verify if the network is
sending B8ZS. If so, and the B8ZS suppression is not set (SW1-5, 6), the B8ZS will be seen as bipolar
alarms, and recorded as such, even though they are not,
SW2-7, 8 are manual loopback requests for diagnostic reasons. Local loopback verifies the ability of the
DXPT1 to sync on itself to insure frame syncing problems are not caused by the DXPT1 board. These
switches are rarely used to enable remote loopback and payload loopback.
NOTE: A local loopback will disable the synchronization card reference causing an automatic switch to
the next reference. If only one reference is configured, the system defaults to the DXP Plus fixed
oscillator on the services board.
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							2.3 Selecting Functions With DIP Switches LIU-1 Through LIU-4
There are four LIU switches. The first switch will change the receive sensitivity from -26 dB to -36 dB.
Changing to -36 dB for extra long loops (1 mile) is not recommended unless the DXPT1 will not maintain
frame sync. In the -36 dB setting, noise could be a problem because of increased sensitivity.
The LIU-2 switch sets the transmit signal level. The transmit signal level has nothing to do with the audio
voice levels. The default is manual “on”  and the transmit level is determined by LIU-3 and 4 settings.
LIU-3 and LIU-4 are defaulted “off” which corresponds to 0 dB (strong signal).
For applications where the DXPT1 is directly connected to a nearby repeater, the automatic mode is
preferred (LIU-2=off) to keep from over driving the repeater. Repeaters are very sensitive on their
inputs. In auto mode, the transmit is determined by the receive level according to the following chart:
LIU-3 and 4 are ignored in auto mode.
IF LEVEL RECEIVED ISLEVEL TRANSMITTED IS
0 to -7.5 dB
-7.5 to -15 dB
-15 to -22.5 dB
-22.5 to -26 dB-15 dB
-7.5 dB
-7.5 dB
0 dB
If in auto mode and LIU switch 3 or 4 is changed, a re-sync is required to reset the new setting.
Unplugging the T1 span in and out is an easy way to cause a re-sync.
2.4 Setting Up The DXOPT-SYN Synchronization Card
Program the synchronization card by strapping the two strap blocks on the auxiliary board. A reference
clock from each T1 board is presented. You can strap the board so that one T1 clock source is the primary
clock reference, and another T1 source is the secondary clock reference. The secondary clock reference is
then used in case the primary span fails. If only one T1 board is installed, we recommend that you strap
the auxiliary board so that the one T1 source is serving as both the primary and secondary reference.
Otherwise, don’t strap the secondary strapping block. See section 4, Installing The DXPT1 Digital Carrier
Transmission Option, IMI89–193. The green LEDs on the sync card verifies the presence of a reference
source. If the green LEDs are off, check the straps, and make sure that the DXPT1 board is not in the
local loopback mode.
If one or more of the green LEDs are lit, the sync card’s red LED (Unlocked) should be off. Do not place
the sync card’s switch in the manual mode during normal operation. The manual mode switch is for
maintenance when you want to force the use of the primary or secondary reference. The automatic mode
allows automatic selection of the secondary reference in the event that the primary reference is lost. If the
sync card does not synchronize, and the green LEDs are lit, the synchronization card is probably bad. The
only other possibility is that the sync card detection circuit on the services board is not working, which is
unlikely. If the DXPT1 board is in an expansion cabinet, be sure the interface boards are multilayer (that
is, not transparent). Earlier interface boards, of the non-multilayer type, are subject to electrical noise.
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							3 Troubleshooting The Protocol Layer
Four protocols are supported:
·E & M
·DID
·Ground Start
·Loop Start
Ground and loop start are subscriber-end only (DXP Plus end) not office-end (network end).
Before starting protocol layer troubleshooting, make sure you have completed all physical layer
troubleshooting to ensure that no alarms are occurring and that the DXPT1 board has no red LEDs lit
except for the large status LED.
Troubleshooting the protocol layer consists of checking the A and B transmit and receive signalling bits.
Depending on the protocol that is active and on which function is occurring, A and B signalling bits can
be a digital one (“1) or a zero (”0). In some cases, the level (“0 or ”1) doesn’t matter and could be
either one (X). These levels are designated by a “0,” “1,” or “X” in the following tables.
When the function involves a user dialing a number with a rotary dial, the signalling bit designated by
“DP” in the following tables, represents the dial pulse (make= 1 ; break = 0). For a ground start protocol,
the signalling bit representing a dial pulse will be a digital one (“1) when a tone dial is used in place of a
rotary dial.
NOTE: In the table below, an X is a don’t care. Signalling can be a 1 or 0. DP is a dial pulse (make = 1,
break = 0).
3.1 Defining The Signalling Bits For The E & M Protocol
FUNCTION TRANSMIT RECEIVE EIA/TIA 464-A
STANDARD
^ABAB^
OUTGOING CALL
Idle
DXP off-hook
Wink
Wink
Dial pulsing
Wait for ANS
Far end ANSW
INCOMING CALL
Idle
CO goes off-hook
DXP sends wink
DXP after wink
Far end DP
Far end wait FR ANS
DXP answers call0
1
1
1
DP
1
1
0
0
1
0
0
0
10
1
1
1
DP
1
1
0
0
1
0
0
0
10
0
1
0
0
0
1
0
1
1
1
DP
1
1X
X
X
X
X
X
X
X
X
X
X
X
X
XWink on
Wink off
Make=1, Brk=0
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							3.2 Defining The Signalling Bits For The Direct Inward Dial (DID) Protocol
FUNCTION TRANSMIT RECEIVE EIA/TIA 464-A
STANDARD
ABAB
INCOMING CALL
Idle
CO goes off-hook
DXP sends wink
DXP after wink
Far end DP
Far end wait FR ANS
DXP answers call0
0
1
0
0
0
10
0
1
0
0
0
10
0
1
1
DP
1
1X
X
X
X
X
X
XMake=1, Break=0
3.3 Defining The Signalling Bits For The Ground Start Protocol
FUNCTION TRANSMIT RECEIVE EIA/TIA 464-A
STANDARD
ABAB
OUTGOING CALL
Idle
PBX grounds ring
PBX grounds tip
PBX removes ring ground
PBX loop closed
Dial pulsing
Dialing CMPL
INCOMING CALL
Idle
CO grounds tip
Ringing interval
PBX presents call
PBX answers call
Normal talking STAT
DISCONNECT PBX
Talking state
PBX opens loop
CO removes tip ground
CO ABANDONS INCOM...
Talking State
CO removes tip ground
PBX opens loop
PBX ABANDONS BEFORE
CO HAS RETURNED TIP
GROUND
PBX waiting tip ground
PBX removes ring ground0
0
0
0
1
DP
1
0
0
0
0
1
1
1
0
0
1
0
0
0
01
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
11
1
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
1
1X
X
X
X
X
X
X
X
1
0
1
X
X
X
X
1
X
1
1
X
X“1 vs DP for DTMF
Idle state
CO hangs up
Idle state
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							3.4 Defining The Signalling Bits For The Loop Start Protocol
FUNCTION TRANSMIT RECEIVE EIA/TIA 464-A
STANDARD
ABAB
OUTGOING CALL
Idle
PBX loop closed
PBX pulsing
Dialing CMPL
INCOMING CALL
Idle
CO sends ring
Interval between ring
PBX presents call
PBX answers call
Normal talking STAT
DISCONNECT PBX
PBX opens loop
Idle
CO ABANDONS INCOM...
CO applies ring
Interval between ring
CO abandons
PBX stop presenting0
1
DP
1
0
0
0
0
1
1
0
0
0
0
0
01
1
1
1
1
1
1
1
1
1
1
1
1
1
1
10
0
0
0
0
0
0
0
0
0
0
0
0
0
0
01
1
1
1
1
0
1
1
X
X
X
1
0
1
1
1
Waiting for dial tone
“1 vs DP for DTMF
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							4 Using The Diagnostic Function
The diagnostic function on the DXPT1 board provides a method for obtaining information about the T1
operation. You can do this either on-site or from a remote location by sending and receiving coded
messages. Remote operation is described in section 4.8.
4.1 Understanding The Diagnostic Switches And Indicators
The diagnostic portion of the DXPT1 board contains eight DIP switches, eight green LEDs, and a “clear”
pushbutton for clearing functions. Set the DIP switches to request certain T1 system information. When
testing from a remote location, using a computer and modem, you can similate the switch settings by
sending a coded message.
The system responds to your request for information by
lighting certain LEDs to provide you with the requested
information. If you are testing from a remote location,
the system responds by sending a coded message that
similates the lighted LEDs.
Use the clear pushbutton to stop any counting function
(denoted by the LEDs sequencing) and reset the counter.
The diagnostic port is a monitor mode only access. You
cannot cause harm to the equipment by moving the
switches or pushing the clear pushbutton. Leaving any
of the switches on will not cause any operational
problems.
Since the operation is cryptic, the customer normally
doesn’t use the diagnostic monitor. Functions of the port
are to simplify problem solving in the field
4.1.1 Determining Channel Number
The letters ABCDE in switch positions 4 through 8 are
used to designate a channel number in many of the tables used on the following pages. See the table
below for the relationship between the letters ABCDE and channel numbers 1 through 24. (Example, a
DIP switch setting of 10100101 requests trunk assignments on channel 6).
CHANNEL A B C D E CHANNEL A B C D E CHANNEL A B C D E
1
2
3
4
5
6
7
8OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFFOFF
OFF
OFF
OFF
OFF
OFF
OFF
OFFOFF
OFF
OFF
OFF
ON
ON
ON
ONOFF
OFF
ON
ON
OFF
OFF
ON
ONOFF
ON
OFF
ON
OFF
ON
OFF
ON9
10
11
12
13
14
15
16OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFFON
ON
ON
ON
ON
ON
ON
ONOFF
OFF
OFF
OFF
ON
ON
ON
ONOFF
OFF
ON
ON
OFF
OFF
ON
ONOFF
ON
OFF
ON
OFF
ON
OFF
ON17
18
19
20
21
22
23
24ON
ON
ON
ON
ON
ON
ON
ONOFF
OFF
OFF
OFF
OFF
OFF
OFF
OFFOFF
OFF
OFF
OFF
ON
ON
ON
ONOFF
OFF
ON
ON
OFF
OFF
ON
ONOFF
ON
OFF
ON
OFF
ON
OFF
ON
T1005
DiagnosticsLED 1
LED 8Clear
Switch 1
OffOn
Switch 8
DXPT1 Diagnostic Switches And Indicators
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							4.2 Requesting Cold Start Information
When the DXP-T1 system is turned on, internal self-tests are run to determine the condition of the
system. When you use this request, you are asking the system to provide you with the results of these
tests. Upon making the cold start information request, the system verifies the following.
·operating mode is superframe (SF) or extended superframe (ESF),
·FDL daughterboard (used for ESF) is installed on the T1 board and okay or not installed (or defective),
·channel capacity currently selected is 8, 16, or 24 channels,
·static RAM is okay or has read/write errors,
·internal CPU RAM is okay or has read/write errors.
4.2.1 Setting The DIP Switches For Cold Start Information
Set the DIP switches as shown in the following table. Switch 1 is the top switch. When the switch is
moved to the right, it is turned on. The hex code shown is used for remote operation only.
SWITCH SETTINGSTYPE OF REQUEST HEX
CODE
12345678Provide results of all self-tests run during
system start-up (cold start). E1
ONON ON OFF OFF OFF OFF ON
^
4.2.2 Reading The Cold Start Information From The LEDs
The Table below shows the cold start information that is revealed by the LEDs. LED 1 is at the top.
LEDs
LED DEFINITIONS
12345678
^
OFF
OFF
ON
OFF
OFF
ON
OFF
OFF
ONOFF
ON
OFF
OFF
ON
OFF
ONNot used
SF mode
ESF mode
Always off
Either in SF mode or FDL board missing or bad
FDL board recognized (ESF only)
Selected channel capacity is 24
Selected channel capacity is 8
Selected channel capacity is 16
Static RAM has read/write errors
Static RAM is okay
Internal CPU RAM has read/write errors
Internal CPU RAM is okay
Example: If you see the following LED light pattern, you can determine the cold start results from the above
LED definitions. (For remote testing, the lFDL board recognized system would send hex code 53.)
m= LED off and|= LED on
m
|= ESF mode
m
|= FDL board recognized
m= 24-channel
mcapacity
|= static RAM fully operational
|= internal CPU RAM fully operational
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							4.3 Requesting Information On Received Signal Strength
When you use this request, you are asking the system to provide the signal strength of its received signals.
Upon making the received signal strength request, the system supplies you with the following information:
·the range in dB of the received signals.
4.3.1 Setting The DIP Switches For Received Signal Strength Information
Set the DIP switches as shown in the following table. Switch 1 is the top switch. When the switch is
moved to the right, it is turned on. The hex code shown is used for remote operation only.
SWITCH SETTINGSTYPE OF REQUEST HEX
CODE
12345678Provide the dB range of the received signal
strength. FF
ON ON ON ON ON ON ON ON
^
4.3.2 Reading The Received Signal Strength Information From The LEDs
The Table below shows the received signal strength information that is revealed by the LEDs. LED 1 is at
the top.
LEDs
LED DEFINITIONSHEX
CODE
12345678
^
LEDs 1 through 4
not used (off)OFF
OFF
OFF
ONOFF
OFF
ON
ONOFF
ON
ON
ONON
ON
ON
ON-7.5 to -15 dB (medium signal)
-15 to -22.5 dB (weak signal)
-22 dB and below (spec is to -26 dB)
(very weak)
0 to - 7.5 dB (strong signal)01
03
07
0F
NOTE: If signal is very weak from a long span of a mile or more, and frame synchronization is not being
maintained, turn DIP switch LIU-1 on.
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