Mitel Sx 50 Dpabx Instructions Guide

							Engineering Information 
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180 6-2 Revision 0 9104-091-l 80-NA Issue 5  
						

							7 . 
TRUNK OPERATION 
LS/GS Trunk Card Operation - Loop Start 
7.1 To place an outgoing call, the trunk circuit places a termination across the Tip and 
Ring leads. The CO detects the current flow and responds with dial tone. The user 
can now dial digits. 
The trunk circuit recognizes an incoming call when it receives ringing voltage or battery 
reversal from the CO. The trunk circuit responds by placing a termination across the 
Tip and Ring leads. The system releases the trunk by breaking the loop current, which 
occurs when either party goes on-hook or when the line is physically broken. 
LS/GS Trunk Card Operation - Ground Start 
7.2 To place an outgoing call, the trunk circuit grounds the Ring lead. The CO responds 
by grounding the Tip lead and sending dial tone. The trunk circuit then places a 
termination across the Tip and Ring leads and removes the ground from the Ring 
lead. The CO is now ready to receive dialed digits. 
The trunk circuit recognizes an incoming call when the CO grounds the Tip lead. The 
CO may also send ringing voltage. The trunk circuit responds by placing a termination 
across the Tip and Ring leads. The trunk is released when the loop current is broken. 
This occurs when either party goes on-hook or the line is physically broken. 
E&M Trunk Module Operation 
7.3 Type 1 and 5 interfaces differ in the signaling applied to the E and M leads. Table 7-l 
shows the switch settings for Type 1 and Type 5 interfaces. The switches are found 
on the E&M Trunk Module. 
(a) Type 1 operation: 
The E&M Module signals the off-hook condition by applying -48 volts to the M 
lead; the far end signals the off-hook condition by grounding the E lead. The E&M 
Module signals the on-hook condition by leaving the E lead open; the far end 
signals the on-hook condition by grounding the M lead. 
(b) Type 5 operation: 
The E&M Module signals the off-hook condition by grounding the M lead; the far 
end signals the off-hook condition by grounding the E lead. The E&M Module 
signals the on-hook condition by leaving the E lead open; the far end signals the 
on-hook condition by leaving the M lead open. 
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							Engineering Information 
Table 7-l E&M Trunk Module Switch Settings 
Function Switches 
12345678 
Signaling 
Type 1 
Type 5 
x x x x x 1. x x 
xxxxxoxx 
PABX to Line Gain 
3 dB 
-13 dB oxxxxxxx 
lxxxxxxx 
- ‘, 
Line to PABX Gain 
-4dB 
-11 dB xoxxxxxx 
xlxxxxxx 
Termination 
600 52 
Complex xx1 oxxxx 
xx01xxxx 
Transmission 
2-wire 
4-wire xxxxl xxx 
xxxxoxxx 
Note: 0 = Open, 1 = Closed, x = Not Applicable. 
DID Trunk Card Operation 
7.4 In the idle state the DID Trunk circuit applies a battery feed of -48 Vdc to the Ring 
lead and ground to the Tip lead. 
The Central Office (CO) seizes the DID Trunk by placing a termination across the Tip 
and Ring leads. The SX-50 system reverses the polarity of the battery feed to 
acknowledge the seizure, depending on the type of supervision selected. The SX-50 
system supports immediate Dial, Delay Dial or Wink Start supervision. DTMF, loop-dial 
or battery-and-ground pulse.dialing from the CO specifies the required extension. The 
battery feed remains in the reverse state for the duration of the call. 
Either end can disconnect the call: 
(a) DID Circuit Disconnect: 
The SX-50 DID trunk circuit reverts to forward battery feed, the idle state. The CO 
removes the termination. Current no longer flows in the circuit. 
(b) Central Office Disconnect: 
The Central Office removes the termination. Current no longer flows in the circuit. 
The SX-50 DID trunk circuit returns to forward battery feed. 
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							- 8 
’ UNIVERSAL CARD MODULES - 
OPERATION 
RMATS Module Operation 
8.1 The UART converts the parallel data on the Universal Card data bus to the serial 
format required by the modem. The output of the modem is one of two audio tones, 
depending on the logic level at the input. A MITEL Codec converts this to the digital 
audio coding used within the SX-50 system. 
Signals coming from a remote terminal’s modem are first digitized by the ONS Line 
Card (or LS/GS Trunk Card) before routing to the RMATS Module. At the RMATS 
Module, the Codec converts the signal back into the analog audio tones for input to the 
modem. The modem outputs the corresponding serial data. The UART converts this 
to parallel data and transmits it on the Universal Card data bus. 
Music on Hold/Pager Module Operation 
8.2 There are two methods of providing Music on Hold/Pager capability in the MS53 and 
MS54 release; 
l A Music on Hold/Pager Module can be installed on the Universal Card 
l The Control Card 2 (MCC2), which incorporates the Music/Pager circuit can be in- 
stalled on the SX-50 DPABX. 
For further information on the Control Card 2 (MCC2), refer to Section , 
9104-091-l 00-NA, General Information or Section 9104-091-200-NA, Shipping, 
Receiving and Installation. 
When a Music on Hold/Pager Module is mounted on the Universal Card, the music 
source is connected to the SX-50 system by a Tip/Ring pair. The installer determines 
which pair from the Tip and Ring Assignments table in Section 9104-091-200-NA, 
Shipping, Receiving and Installation. 
The music input is a transformer with an impedance of 150 . The input signal should 
be between 50 and 500 mVrms. High frequency attenuation and amplitude limiting are 
applied as required by FCC rules, Part 68. The maximum input level before amplitude 
limiting occurs is approximately -6 dBm. 
The paging output is transformer-coupled and has an impedance of less than 200. The 
output level into a 600 load is typically -6 dBm. 
A relay is provided to control an external paging amplifier. Its contacts are rated as follows: 
l maximum switching voltage - 90 Vrms 
l maximum carrying current - 0.4 Amps. 
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							_ 9 
’ DIGITAL SWITCHING MATRIX 
DESCRIPTION 
General 
9.1 The SX-50 system accepts analog voice signals at its line and trunk inputs, converts 
them into digital signals and passes them to the Digital Switching ,Matrix. The method 
. . ._ 
of conversion is Pulse Code Modulation (PCM). Tim+Drvrsron-Multiplexing (TDM) is 
used to combine many signals for transmission over a few single links within the 
system. The signal is routed via these links to its destination - usually a line card or a 
trunk card - where it is reconverted to an analog signal. 
Pulse Code Modulation 
9.2 PCM uses the following procedures: 
l sampling, 
l quantizing, 
l encoding. 
Sampling determines the amplitude of the analog signal at a point in time (actually, over 
a very short time period). The sampling process is repeated at a rate twice the highest 
frequency to be encoded. In the SX-50 system, sampling occurs at a rate of 8 kHz, 
permitting accurate encoding of signals with frequency components up to 4 kHz. 
Quantizing and encoding assign 8-bit binary values to each sampled amplitude. 
Errors 
occur when: 
l the sample amplitude falls between two binary values, 
l the sample amplitudes are below the lowest binary value. 
Companding partially compensates for these errors by encoding and decoding the 
sample values on a non-linear scale. A given change in the level of a small signal 
causes a proportionately larger change in the sample’s binary value than would the 
same change in the level of a large signal. There are two different companding scales: 
PLaw and A Law. PLaw is the North American standard; A Law is the European 
standard. . 
Time-Division-Multiplexing 
9.3 Time-Division-Multiplexing (TDM) transmits several channels of information over the 
same path by allocating a different time slot for each channel. 
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							Engineering Information 
A Link is divided into 32 channels, each assigned a time slot. Each channel, depending 
on its source; may carry PCM-encoded audio or control data. The information on each 
channel is provided in 8-bit binary samples (bytes), as previously discussed. Since the 
sampling rate is 8 kHz, on any given channel a new sample is encoded every 125 ps. 
During each 125 p.s period, the TDM circuitry transmits the most recent 8-bit sample 
from each of the 32 channels in turn. Each group of 32 samples is called a frame. 
Communication on any particular channel requires that the transmission circuitry insert 
each sample into the correct time slot in each frame sent, and that the receiving circuitry 
extract the information from the correct time slot in each arriving frame. 
The system bit rate can be derived as follows: 
8000 frames/second x 32 channels/frame x 8 bits/channel 
= 2,048,OOO bits/second 
= 2.048 Mbits/second. 
Digital Switching Array 
9.4 The Digital Switching (DX) Array assigns 1.5 bidirectional links (48 channels) for 
transmitting and receiving audio, control and signaling data to and from the 
peripheral card. 
The DX Matrix transmits 3 bytes per frame to each peripheral circuit: one PCM audio 
and two control bytes. One control byte adjusts the gain of the peripheral circuit; the 
other provides control signals for ringing-and supervision. 
The Digital Switching Array also assigns the following links: 
l 1 link (32 channels) for receiving audio from the Console and signals from the Digital 
Signal Processor, 
l 1 link (32 channels) for transmitting audio to the Console and to the Digital Signal 
Processor, 
l 1 link (32 channels) for transmitting control data to the Console and audio to the 
DTMF Receivers. 
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							10 . 
TRAFFIC CONSIDERATIONS 
General 
10.1 This Part provides data used in determining traffic-dependent parameters. These 
parameters are: 
l Quantities of trunks installed. 
l Level of traffic per line. 
l Level of traffic per system 
Reference tables assist in estimating the SX-50 hardware requirements for a range of 
typical applications. Table 10-l is used to determine the station traffic characteristics 
of a business. Table 10-2 provides the maximum allowable station traffic for 
configurations from 8 to 128 extensions, 16 to 32 trunks. 
Traffic Parameters 
10.2 Traffic engineering is a statistical method used to ensure that you have provisioned 
your system to give the level of service to which your users are accustomed. 
Understanding these traffic engineering concepts is important when purchasing or 
configuring your PBX. 
Use the traffic report figures as guidelines. Specific departments or trunks may not 
follow the averages of the rest of the system. This should be understood and analyzed 
to ensure that your system can meet the needs of all users. 
The following assumptions have been provided to aid in configuring your system: 
(a) Traffic patterns are approximately: 
l 33% internal 
l 33% outgoing 
l 33% incoming 
(b) Trunks are both-way, as these are most efficient for carrying traffic. 
(c) Target grade of service is P.01 or the same as the level which most telephone 
companies provide. 
To determine your average traffic levels for a particular business hour of the day, divide 
the number of calls for this hour by the number of telephones on your system. 
l one call per hour = light traffic 
l two calls per hour = medium traffic 
l three calls per hour = heavy traffic 
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Typical Station Traffic Characteristics 
10.3 The provisioning of an SX-50 system for a particular application depends upon the 
average station usage (traffic), as characterized by two parameters: 
l Traffic per station (Busy Hour, Busy Day) 
l Percent Trunk Traffic (versus intercom). 
The traffic per station depends upon how much the average job function in the business 
requires the use of a telephone. For example, a regional wholesale distributor may 
have a large group of buyers and salespersons handling outside calls, and therefore 
have a relatively high traffic per station (5 -+ 7 ccs/station). 
The division between internal intercom and trunk traffic is related to the density of 
telephones. For example, in professional or service industries where employees are 
close enough to speak to each other in person, intercom traffic is low (i.e., Trunk traffic 
70% - 90%). In department stores or manufacturing sites where employee and 
telephone density is low, the proportion of intercom calls would be higher. 
As a guideline, Table 1 O-l provides typical station traffic characteristics for a number 
of potential SX-50 applications. Used in conjunction with the customer’s specific 
requirements, and Table 1 O-2, System Traffic, it is possible to determine the number 
of CO Trunks required, given the number of station sets and SUPERSET telephones 
in the system. 
Table 1 O-l Typical Traffic Characteristics 
SX-50 Applications 
- Engineering 
- Finance 
- Real Estate 
- Stock Broker 
*depending on application 
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Table 1 O-2 System Traffic 
Maximum System Traffic per Line (CCWLine) 
COV/DNIC* 0 8 16 
24 32* 40 48 56 
TRK 
ONS 
16 0 - 36.0 25.3 16.8 12.6 10.1 6.5 3.9 
16 16 25.3 16.8 12.6 10.1 8.4 5.9 3.9 2.3 
16 32 12.6 10.1 8.4 7.2 5.5 3.8 2.5 - 
16 48 8.4 7.2 6.3 5.1 3.7 2.6 - - 
16 64 6.3 5.6 4.7 3.6 2.6 - - - 
16 80 5.1 4.4 3.5 2.7 - - -  T 
16 96 4.2 3.4 2.7 _ _ -_ _ - 
16 112 3.3 2.7 - - _ _ _ - 
, 
16 128 2.6 
_ _ - _ _ - _ 
24 0 - 36.0 36.0 21.9 13.6 8.5 5.2 2.8 
24 16 31.7 22.3 15.4 10.7 7.4 4.9 3.0 - 
24 32 14.9 11.7 8.8 6.5 4.6 3.0 - - 
24 48 9.3 7.5 5.8 4.3 3.1 - - - 
24 64 6.5 5.3 4.1 3.0 - - - - 
24 80 4.8 3.9 3.0 - - - _- - 
24 96 3.7 3.0 - - - - - - 
24 112 2.9 - - - - - - _ 
32 0 - 36.0 34.7 19.3 11.5 6.9 3.8 - 
32 16 29.0 20.1 13.7 9.3 6.1 3.8 - - 
32 32 13.6 10.5 7.7 5.5 3.7 - - - 
32 48 8.4 6.7 5.0 3.6 - - - - 
32 64 5.8 4.6 3.5 - - - - - 
32 80 4.3 3.4 - - - - - - 
32 96 3.3 - - - - - - _ 
* Maximum number of DNIC cards allowed is 4. 
1: Intra/lncoming/Outgoing ratios are: 21% : 41% : 38% 
2: Intra/lncoming/Outgoing call hold times are: 88/ 175/ 135 (seconds) 
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