GTE Omni Si Database Technical Practices Issue 1 Manual

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							TL-130500-1001Blockage10.3.2 Blockage can only occur when the number of voice
Occurrencetraffic line and trunk circuits in a PCMUS group exceeds the
number of available time slots. Since it is unlikely that all the
time slots in a PCMUS group will be busy simultaneously for any
length of time, blockages rarely happen. To further reduce the
possibility of blockage, a simple traffic study (traffic engineering)
should be done. This will prevent putting too much hardware into
a group. Traffic engineering is explained in the next paragraph.
Traffic10.3.3 Traffic engineering compares the amount of hardware
Engineering(line and trunk) used against the amount of time slots available to
determine if blocking will occur. Traffic engineering should be
done before installation and if any additions are made to the
system.
Determining10.3.4 If actual traffic data is not available to calculate the
Blockageprobability of blockage for a PCMUS group (the P level). it will
Probabilitybe necessary to make some assumptions about the line and
trunk usage for the group. A catalog department would create a
heavy usage for the associated lines and trunks, while a group of
mid-level executives are likely to be a light load in comparison.
These estimates permit the installer to make a preliminary card
layout. Later line and trunk usage can be empirically measured
to fine tune the card layout.
The standard measure of traffic in the United States is the CCS
(Hundred Call Seconds). One call which lasts for 100 seconds
constitutes one CCS, 60 seconds x 60 minutes = 3600 seconds
in one hour =36 hundred call seconds in one hour. Example 
-
18 CCS = 30 minutes; 9 CCS = 15 minutes; 6 CCS = 10
minutes. Based on experience, a number of CCS can be
assumed for a line or trunk according to its expected usage.
Table 10.1 summarizes these levels.
Table 10.1Estimated Traffic Equivalents
I
USAGE LEVEL
k .*-*,,-
---+
LINE CCSTRUNK ccs
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Determining10.3.5 (Figure 10.4) To calculate the estimated usage of a
CCS UsagePCMUS group:
of a System1. Multiply the number of lines by the letermined CCS value.
2. Multiply the number of trunks by the determined CCS value.
NOTE: Because DID and DOD trunks are one way, they can be
considered low traffic.
3. Add these totals together.
(L X 
CCS/L) + (T X CCS/T) = CCSigroupL = total lines in the group
T=total trunks in the group
NOTE: Calculate all circuits on a line or trunk card, whether in
service or not. In case of expansion, this prevents having to
reconfigure the system.
Because the offered CCS for each time slot group is 529, the
total CCS output for the hardware located in each group cannot
go over 529 CCS.
(L X 
CCSL) + (T X CCS/T) = or C 529
Example: Determine traffic volume for group A.
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							TL-4 30500-l 001Dedicated10.4 Certain equipment must have a time slot reserved for its
Time Slots
use at all times (this is called a dedicated time slot). Each
dedicated time slot is effectively removed from the pool of time
slots associated with a PCMUS group.
The Attendant Console requires a dedicated time slot because
the attendant must be accessible at all times. Dedicated time
slots affect the traffic handling capacity of a PCMUS group.
Table 10.2 lists the equipment that uses dedicated time slots.
Each Attendant Console requires a PLCC line circuit for voice
connection. The line circuit uses a dedicated time slot. The
music-on-hold feature also requires a PLCC line circuit which
uses a dedicated time slot.
Off-hook queuing takes a time slot. Do not take this into
account when doing a traffic study; however, it should be
considered when setting data base parameters 
- as too many
calls in a queue can affect the traffic of the system.
Table 10.2Equipment Utilizing Dedicated Time Slots in a PCMUS Group
IN-SERVICE EQUIPMENTNUMBER OF DEDICATED TIME SLOTS
PER CIRCUIT
DMTF Receiver Circuits
Attendant Line Circuits
Music-on-Hold Line Circuits
Release Line Trunk Circuits
Recorder Announcer Trunk Circuits
Guaranteed Access Trunk Circuits
Nailed Trunk Circuits (both)
Progress Tone Circuits
TOTAL DEDICATED TIME SLOTS
NOTE: A NIC card is one end of a
nailed trunk connection
NOTE: Table 10.2 can be used to add the total number of
dedicated time slots in a PCMUS group.
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							TL-130500-1001Progress Tone10.4.1 Access to a PPTR (FB-17280-A) card circuit is
Recognizerrequired for stations allowed to access an SCC through MEW(Most Economical Route Selection).
The system supports a maximum of two cards with four circuits
per card. Each circuit of the PPTR requires a dedicated time
slot.The number of stations using the feature determines the
number of circuits used (Table 10.3).
Table 10.3Required PCM Progress Tone Recognizer PCBs
Number of PCM Progress
Tone Recognizer
Circuits RequiredNumber of FB-4 7280-A
PCBs Required
Maximum Number of
Stations Allowed
MERS SCC Access
NOTES:
0 This table is based on a nominal holding time of 8 seconds. It
is recommended that all PPTR 
PCBs be spread evenly
throughout the system.
@ The previous table is for reference only; for specific
applications, a traffic study 
sqould be performed.
* Each PPTR circuit enabled utilizes a dedicated time slot.
DTMF (Dual Tone10.4.2 The following require access to a DTMF circuit:
Multi-frequency)
0 All telephones except the Integrated Featurephone (analog,
digital, and rotary)
- The DTMF card converts analog signals into digital signals.
- Analog to digital conversion for an Analog Featurephone is
done on the PLCC. For the Digital Featurephone, this is
done at the phone.
l Attendant Console
- The Attendant Consoles in the system share a dedicated
circuit on one of the PDTMF receivers; the rest of the
system must share the remaining circuits.
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l CAS Branch system with DTMF stations- DTMF receivers should be provided for each E&M Tie trunk
(FB-17201 -A or FB-51267-A)
- Each Tie line (E&M circuit) will be counted as two more
DTMF stations
- Each Tie line (E&M trunk circuit) that sends PDTMF signals
to the PABX will be counted as two more PDTMF stations
To determine additional 
PDTMFs required for release link trunks
in the CAS Branch option, see Table 10.4.
Table 10.4
Required PRLT CircuitsPRLTPRLT
PDTMF
CircuitsRequired
PCBsReceiversPCBS
1111
2121
3131
4141
5252
6252
7262
8262NOTE: The system has a limit of 8 DTMF receiver circuits.
The system maximum for DTMF cards is two with four circuits on
each card. The number of circuits required to support the
system can be determined in one of two ways:
l By the number of stations requiring access to DTMF circuits
l By the traffic in CCS for lines and trunks accessing the DTMF
receivers.
Determining DTMF10.4.3 Table 10.5 provides the number of DTMF cards and
Circuits by Numbercircuits per card required to support a given number of
of Stationstelephones. Example 
- 150 telephones would require five
circuits on two cards.
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							TL-130500-1001Table 10.5Required PDTMF Receivers
Number of PDTMFsFB-17203-A
Maximum Number of
(TCR Circuits)PDTMF 
PCBs RequiredPDTMF Stations
2717
3
156
4
1111
52176
62250S-l 60
NOTES:
0 This table is based on 3.75 originating calls per PDTMF
station, and eight seconds holding time.
l This table is used only to determine the number of circuits
used by telephones.
The total quantity of PDTMF receivers is established by adding
all PDTMFs required for stations, CAS Tie trunks, PRLTS (PCM
release link trunks), Attendant Consoles, and Agent Instruments.
DTMF10.4.4 When a DTMF receiver is not available to a user,
Receiverblockage occurs. The CAS Agent Instruments and Tie lines
Engineeringwhich are offered dial access into the system are heavy DTMF
receiver users. This is due to their concentration of calls into the
system. To compensate for this, two DTMF receivers are
reserved for CAS operation (if implemented).The remaining
users must be considered by the system planner.
The DTMF signaling lines, incoming tie, DID, and CCSA
(Common Control Switching Arrangement) trunks generate traffic
to DTMF receivers. The formula for determining DTMF receiver
traffic generated by DTMF lines is as follows:
(Number of originating DTMF lines x originating calls per
DTMF line) x (DTMF receiver holding time per call)/100 =
DTMF receiver traffic in CCS.
The formula for determining DTMF receiver traffic generated by
incoming trunks presenting DTMF signals to the system is as
follows:
(Number of incoming DTMF trunks) x (Incoming calls per
DTMF trunk) x (DTMF receiver holding time per 
call)/100 =
DTMF receiver traffic in CCS
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One additional receiver must be provided with each of the first
two 
RLTs if the CAS Branch option is used. These DTMF
receivers are dedicated to the 
RLTs. The remaining RLTs share
the pooled DTMF traffic with the lines and trunks, and the 
RLTsmust be considered in sizing the receiver pool. Any receiver can
be used for line and trunk DTMF receiver traffic use, but by
reserving two receivers (for 
RLTs), lines and trunks cannot
exhaust the available supply of receivers.
Determine the DTMF receiver traffic load for the various sources.
The total of these values determines the number of DTMF
receivers required. The typical busy-hour parameters for a line
are 3.75 originating calls per line per hour with an &second
DTMF receiver holding time, each equal to a 0.3 CCS traffic load
per line. The typical busy-hour data for a one-way incoming
Tie trunk is 12 originating calls per trunk with a 3-second DTMF
receiver holding time, which is equal to a 0.36 CCS traffic load
per trunk. Thus, if 100 lines were installed, a load of 30 CCS
would be presented to the DTMF receivers and 
‘0 DID trunks
would bring the total to 33.6 CCS. Table 10.6 defines the DTMF
receivers required to support various amounts of traffic.
Determining10.4.5 A typical line, during its peak traffic period, accesses
DTMF Circuitsa PDTMF circuit 3.75 times per hour. The average holding time
by CCS Countfor each access is 8 seconds. This is equivalent to 0.3 CCS.
Similarly, a typical trunk arranged to receive DTMF will create a
0.36 CCS load at its peak traffic load. Use the following formula
to determine the peak load presented to the PDTMF circuit.
(L x 0.3 CCS) + (T x 0.36 CCS) = PDTMF Load
Table 10.6 provides a guide to help determine how many PDTMF
receivers are needed to avoid potential congestion.
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							TL-130500-1001Table 10.6DTMF Receivers Required to Provide aP=
0.01 Grade of Service
Traffic In CCSDTMF Receivers Required
5.32
17.03
33.44
53.05
75.06
99.0
7
124.08
NOTES:l The actual probability of a delay greater than 3 seconds =
0.005.l The 
CCSlline and CCSitrunk values used in this example are
assumed; actual value will vary from system to system.
0 The Eight-Party Conference card uses up to eight time slots
when fully loaded, but typically requires five time slots.
0 The typical busy-hour parameters for a one-way incoming
trunk (DID) are 12 originating calls per trunk with a 3-second
DTMF receiver holding time, which equals to a 
0.36-CCStraffic load per trunk.
If 100 lines are installed, a 30 CCS load is presented to the
DTMF receivers and 10 DID trunks brings the total to a 33.6 CCS
load.Recommendations for placing the DTMF cards are as follows:
* The first DTMF card normally is placed into card slot AO.
l When a second DTMF card is required, it is put into the
Expansion File, normally into group C2 (C7 
- Cll). Group C2,
which only has five slots, offers the best ratio of time slots
because it has the smallest number of physical slots.
l If a circuit on a DTMF card is not currently in service, but
customer growth may cause it to be put in service, it should be
counted in the traffic study to prevent having to reconfigure the
system at a later time.
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