Comdial Dxp Plus Instructions Manual

Installing The DXPT1 Digital Carrier Transmission Option
In The DXP Plus Digital Communications System
1.0 Introducing The DXPT1 Option
The digital carrier transmission option (DXPT1) gives the DXPPlusdigital communications system the
capability to handle up to 24 channels of voice and/or data transmissions over a single four-wire cable using
multiplexing techniques in superframe (SF) or extended superframe (ESF) format. The DXPT1 board includes a
customer service unit (CSU) to eliminate the need for a...

1.1 Understanding The DXPT1 Board
Through time division multiplexing, the DXPT1 board greatly increases the efficiency and economy of the DXP
Plussystem by providing up to 24 channels on two twisted metallic pairs. This multiplexing technique allows
two-way voice or data communications at 1.544 Mbps (million bits per second) with either a central office (CO),
public branch exchange (PBX), or another digital communications system (DXPPlus). The DXPT1 board
includes a built-in customer service unit (CSU)...

2.0 Installing Circuit Boards In The Equipment Cabinet
CAUTION
Circuit boards are susceptible to damage caused by electrostatic discharge, and you must keep this fact in
mind as you handle the circuit boards. Refer to the Comdial publication IMI01-005,Handling Of
Electrostatically Sensitive Components, for general information. Specific handling precautions are also
included in this installation instruction.
2.1 Creating A Static Safe Work Area
When servicing the common equipment cabinet at the...

3.0 Configuring The DXPT1 Board
Before you install the DXPT1 board, determine if you must meet special system requirements such as fractional
service (8 or 16 channel operation). If you do have special system requirements, use the dual in-line pin (DIP)
switches provided on the board to re-configure the DXPT1 board.
The DXPT1 board contains 28 DIP switches (three 8-position modules and one 4-position module). Rectangular
cutouts in the front-edge panel provide access to these switches.
The eight DIP...

Locating The DIP Switches
T1002A
Reset Pushbutton
(Behind Hole)
LIU
SW1
SW2
00
011
1
(Default)
1
2
3
4(Default)
1
2
3
4
5
6
7
8
(Default)
1
2
3
4
5
6
7
8
(See Table 3)
(See Table 1)
(See Table 2)
Diagnostic
Switches and LEDs
For Factory
Use Only
Installing The DXPT1 Line Board IMI89–193
Installing The DXPT1 Line Board – 5 

3.1 Understanding The T1 Options (SW1–1 Through SW1–8)
The following T1 operating modes are described to help you understand the many options that you can select with
DIP switches SW1–1 through SW1–8 on the DXPT1 board.
3.1.1 T1 General Operation
T1 is the digital two-way transmission of telecommunications over a single high-speed circuit. Up to 24 separate
voice or data transmissions form digital pulses that are transferred at the rate of 1.544 million bits per second
(Mb/s) over the T1 trunk. At the...

3.1.5 Zero Suppression
There are two ways to avoid system timing problems when eight or more successive zero (0) bits are transmitted.
One method is B7 suppression and the other is bipolar 8-zero substitution (B8ZS). For pulse modulated voice
(PCM), eight consecutive zero (0) bits should never occur.
B7 suppression is a technique that forces a one (1) bit in the 7th bit position when all of the bits in a binary word
are zero (0). The resulting distortion in a voice circuit is negligible. However, this...

3.2 Understanding The T1 Options
(SW2–1 Through SW2–8 And LIU–1 Through LIU–4)
The following T1 operating modes are described to help you understand the many options that you can select with
DIP switches SW2–1 through SW2–8 and LIU–1 through LIU–4 on the DXPT1 board. DIP switches designated
LIU are associated with the DXPT1 board’s line interface unit.
3.2.1 Loopback
Loopback is the maintenance routine used to verify the receive function (local or remote) and to isolate system
problems. When using the...

3.2.7 Transmit Level Attenuation
You can manually set the transmit level for a particular value (0, -7.5, -15, or -22.5 dB) or select the automatic
feature that sets the transmit level automatically depending on the receive signal. A weak receive signal causes a
strong transmit signal and vice versa. Use DIP switch LIU–2 to select either the manual or the automatic setting.
If you select the manual setting, set the desired value with DIP switches LIU–3 and LIU–4. Normally, 0 dB is
used when connecting to...

4.0 Installing The DXPT1 Board
1. Normally you should disconnect the AC power cord from the AC outlet and disconnect the optional battery
back-up assembly from the main cabinet power supply; however, when necessary, you can install a DID line
board in an operating system. If you must do this, connect one end of a standard telephone handset coil cord
to the precharge port on the power supply. During step 6, you will connect the other end of this coil cord to
the precharge jack on the line board.
2....