ATT Definity Addendum 1 For Ds1, Dmi, Isdn Pri Instructions Manual

							NETWORK CONNECTIONS AND CONFIGURATIONS2-13
System 85 or Generic 2 ISDN-PRI to Another Vendor’s Digital Switch½
When a System 85 or Generic 2 ISDN-PRI connects to another vendor’s customer-premises switch
(another vendor’s ISDN-PRI or equivalent), several items should be verified to ensure compatibility.
These include the interface electrical characteristics, options, and synchronization capabilities. The
following questions should be answered:
lDoes the vendor product provide a DSX-1 interface?
lDoes the vendor product support at least one each of the line coding, framing, and signaling options
provided by System 85 or Generic 2?
lFor synchronization purposes, what stratum clock does the vendor switch provide?
lWill the vendor switch act as a timing master or slave its timing to the System 85 or Generic 2?
lDoes the vendor switch implement the digital loss plan specified by EIA/PIN-1429?
lCan the vendor switch be administered for either the user side or the network side as required?
lIs call-by-call (CBC) provided and what are the network service values (NSVs) for their services?
lFor CBC, under what conditions are NSVs to be sent?
lFor CBC, can NSVs be sent in the same dial-plan format as other incoming services?
lHow are the messages and digit manipulation schemes implemented?
lHow are the numbering plans implemented?
Depending on the answers to these questions, basic compatibility can be determined.½
½
½
½
½
½
½
ISDN-PRI PUBLIC-NETWORK CONNECTIONS
Public network connections typically involve connecting a System 75, System 85, Generic 1, or Generic 2
to a 4ESS. Refer to System 85 R2V4 to 4ESS Via ISDN PRI Access (555-037-232), DEFINITY
Communications System Generic 1.1 to 4ESS Via ISDN PRI Access (555-037-234), DEFINITY
Communications System Generic 2.1 to 4ESS Via ISDN PRI Access (555-037-235) and Technical
Publication 41459 Integrated Services Digital Network (ISDN) Primary Rate Interface for AT&T
Communications (326-201) for more detailed information on these connections.½
½
½
½
½
½
System 85 R2V4, Generic 1, and Generic 2 to a 4ESS½
Connections to a 4ESS are called special-access connections. The physical connection is made from
customer premises to a 4ESS. Toll calls go directly from the customer premises switch to the AT&T
toll network. Network ISDN features and services are available through a 4ESS. The physical
connection to a 4ESS toll switch is made (through the DIF frame) to a SM9 circuit pack.
ADDENDUM 1 (December 1990) to 555-025-101, Issue 4 
						

							2-14NETWORK CONNECTIONS AND CONFIGURATIONS
Framing, Signaling, and Line Coding
A 4ESS does not place any restrictions on the framing, signaling, and line-coding options. Any
applicable restrictions are related to the application and particular installation.
*
Dial Tone
Second dial tone may be provided by a 4ESS. However, it is recommended that the customer-premises
switch provide a second dial tone. With this arrangement, the second dial tone can be provided through
use of the ARS feature on all ISDN-PRI trunks that terminate on a 4ESS.
Touch-Tone Capability
ISDN-PRI does not support either dial pulse addressing or touch-tone signaling, but provides the
equivalent capabilities with ASCII character signaling on the D-channel.½
Screening Intra-LATA Calls
A 4ESS can be used to block intra-LATA calls. However, all System 75, System 85, Generic 1, and
Generic 2 special-access applications should use the ARS feature to screen outgoing calls. By using the
ARS feature, only inter-LATA calls are routed to a 4ESS.½
NFAS
Nonfacility-associated signaling is supported by a 4ESS. From a Generic 1 (R1V5) and Generic 2
perspective, there are no restrictions with this capability.½
Backup D-Channel
The D-channel backup is supported by the 4ESS. From a Generic 1 (R1V5) and Generic 2 perspective,
there are no restrictions with this capability.½
Codeset
Both 4E11 and 4E12 receive and transmit UUI data in codeset 7.
4E13 receives and transmits UUI data in codeset 6. However, it will still tandem codeset-7 information.½
User-to-User Information transfer
To pass user-to-user information (UUI) through the ISDN public network, all 4ESS-to-4ESS links must
be implemented with CCS7. If as many as one link is implemented with CCS6, then UUI will not be
passed.
ADDENDUM 1 (December 1990) to 555-025-101, Issue 4 
						

							NETWORK CONNECTIONS AND CONFIGURATIONS2-15
Network Specific Facility
A network specific facility (NSF) is an ISDN IE, sent in the setup message, that identifies the network
or feature associated with the call. For outgoing calls from the customer-premises side, the 4E11 and
4E12 will accept a NSF but do not require that one be present for static calls. When connected to a
4ESS, a System 85 R2V4, Generic 1, Generic 2 must send the appropriate NSF for MEGACOM, SDN,
ACCUNET, and switched digital international calls.
NOTE: For Generic 2, MEGACOM 800 service calls do not require an NSF since it is an
incoming-only service which cannot be tandemed to another switch as a MEGACOM 800 call.
For call-by-call trunk groups, the 4ESS will check for a NSF and will reject the call if one is not
present.½
½
½
½
½
½
½
Synchronization
A 4ESS is always synchronized to the AT&T reference frequency. Therefore, for special-access
applications, the System 85 or Generic 2 normally uses a 4ESS as the master-clock source. A particular
ISDN-PRI facility may or may not be selected as the clock reference to the switch, depending on the use
and reliability of other interfaces. The rules and considerations for selecting a synchronization source
are detailed in chapter 5, Synchronization of Digital Facilities.½
½
System 85 R2V4, Generic 1, or Generic 2 to a DACS½
The DACS does not interpret DMI-MOS or ISDN-PRI and does not support those types of connections.
However, D4, ESF, and RBS are supported and DACS will pass PRI.
System 85 or Generic 2 ISDN-PRI to a 5ESS
A 5ESS is most frequently used by a LEC. It provides digital CO services, both to subscribers and
customer premises switches. For ISDN applications, a 5ESS must be equipped with 5e4.2 or later
software.½
½
½
A System 85 or Generic 2 ISDN-PRI connects to the extended digital subscriber line (EDSL) circuit pack
in a 5ESS (only those configured with 5e4.2 Generic implement the network).
A 5ESS may or may not be synchronized to the AT&T reference frequency. A 5ESS has a lower
stratum clock (higher accuracy) than a System 85 or Generic 2. Therefore, this issue should be verified
for each specific configuration.½
½
½
½
ADDENDUM 1 (December 1990) to 555-025-101, Issue 4 
						

							2-16NETWORK CONNECTIONS AND CONFIGURATIONS
ISDN-PRI INTRA-SWITCH CONNECTIONS½
ISDN-PIR links may also be used to connect certain AT&T features to the switch to enhance feature
performance. The following products used ISDN-PRI trunks in this manner.½
½
Generic 2 ISDN-PRI with the Integrated Telemarketing Gateway Interface½
The Integrated Telemarketing Gateway Interface (ITGI) feature provides an interface between a
Generic 2.1 (Issue 3.0) and an Integrated Telemarketing Gateway (ITG). ITG is a hardware and software
package that provides a gateway between the switch and call-center software, enabling the call-center
software to monitor and control certain incoming, outgoing, and internal calls. The ITG software resides
on an AT&T 3B2 computer and the call-center software resides on a separate host computer. Since the
call-center software is not part of the ITGI feature, the customer is responsible for obtaining and
developing this software.½
½
½
½
½
½
½
Compared to a telemarketing operation, a call-center operation has a broader scope. A telemarketing
operation typically handles only incoming calls. A call-center operation handles high volumes of
incoming and outgoing calls as well as call transfers and conferences.½
½
½
Figure 2-1 shows an example of an ITGI configuration. The ITG is a 2-way gateway where information
travels through the ITG from the switch to the call-center software, and from the call-center software to
the switch. Each answering position, typically an ACD agent, has a voice terminal and a data terminal
or a work station with voice and data capabilities.½
½
½
½
Call Management Services
ITGI provides the following call management services:½
½
lIncoming call management
lOutgoing call management
lTransfer and conference management
These call management services enhance agent call-handling capabilities and increase agent productivity½
½
½
in a call-center environment.
For incoming calls, the switch sends call information through the ITG to the call-center software. From
this information, this software determines how to handle the call and what database information to
retrieve for this particular caller. Call-handling information is sent through the ITG to the switch, which
uses this information to route the incoming call to an available agent. Database information, such as a
customer account record or a catalog order form, is automatically routed to this same agent so that it is
instantly displayed as the agent takes the call.½
½
½
½
½
½
½
½
Outgoing calls are handled in a similar way. By way of the ITG, the call-center software sends the
switch instructions for placing a call and the switch sends the call-center software information about the
call. Outgoing calls can be initiated by an agent (using a data terminal) or by the call-center software.½
½
½
ADDENDUM 1 (December 1990) to 555-025-101, Issue 4 
						

							3. DS1 TRANSMISSION AND CABLING
Digital signal level 1 (DS1) is the specification for a particular digital signal format. DS1 interfaces
should not be confused with T1 digital carriers. T1 is a specific transmission system. T1s are used to
transmit digital signals of the DS1/DMI/ISDN-PRI format. This chapter describes the different methods
of transmitting DS1 from one point to another.
A digital transmission network consists of the following four major parts:
lTerminals
lMultiplexers
lCross-connects
lTransmission facilities
Terminals are the endpoints of the network. They generate and terminate digital signals. The
DS1/DMI/ISDN-PRI, channel-division multiplexers (CDMs), and channel-expansion multiplexer (CEMs)
are examples of terminal transmission equipment.
Digital multiplexers provide interfaces between the different bit rates in the digital network. The DS1 is
the lowest level; the DS4 is the highest level. The DS4 contains 4032 64K-bps channels and has a line
bit rate of 274.176M-bps. When a System 75 or System 85 DS1/DMI/ISDN-PRI signal is routed over
facilities provided by a vendor such as AT&T, the signal may be multiplexed on and off higher-rate
digital lines on the way to its final destination. Multiplexers may also be used on customer premises
and in private networks.½
Digital cross-connects are the interconnection points between the cable and the connector for terminals,
multiplexers, and transmission facilities. Specifically, the DS1 cross-connect, called DSX-1, is used to
interconnect DS1s. Several important concepts related to the DSX-1 are as follows:
lConnection to public-network DS1 facilities is made at a DSX-1 cross-connect. This cross-connect
point (and usually the equipment used to terminate a DS1 facility) is the point of demarcation where
customer-premises responsibility for equipment ends and the network provider’s responsibility for
equipment begins.
lThe signal present at the DSX-1 cross-connect differs from the signal on the DS1 transmission
facility in one important respect. The transmission facility carries DC power, which is used to
power line repeaters and network channel-terminating equipment (NCTEs). The signal at the DSX-1
cannot carry DC power.
lThere exists a maximum cable distance from the DS1 (or DS1 terminal equipment) to the DSX-1
cross-connect point (655 feet for 24-AWG cable). However, a cross-connect point is not always
required. An example of when the cross-connect point is not required would be a continuous cable
that directly connects two DS1s. For this case, it is recommended that a phantom point midway on
the cable be selected as the cross-connect point. With this arrangement the maximum permitted
distance between the two DS1s is twice the value specified to a DSX-1 cross connect.
3-1
ADDENDUM 1 (December 1990) to 555-025-101, Issue 4 
						

							3-2DS1 TRANSMISSION AND CABLING
Digital transmission facilities are used to transmit digital signals from one location to another. Many
different digital transmission systems exist of which T1 is one. The type of facility used depends
primarily on the distance between the endpoints, but other requirements may also affect facility
selection. For example, an application may require nonmetallic facilities as opposed to metallic ones for
reasons specific to that application. Examples of some of the DS1 transmission facilities available are
T1 Outstate (T1/OS), FT3 Lightwave, and Microwave Digital Radio (DR-18 or DR-23). Details of these
transmission systems are not provided here.½
Several different interconnection options and considerations exist for a System 75, System 85,
DEFINITY® Generic 1, and Generic 2 for DS1/DMI/SDN-PRI such as cable types, distance limitations,
and switch settings that are unique to the particular unit of equipment. These options and considerations
are described in the following sections.½
METALLIC CABLING OPTIONS
Metallic cable is usually used to connect a DS1 to a DSX-1 cross-connect. Specific cable configurations
depend on the application and if intervening transmission terminal equipment is in use.
DSX-1 Distance Limitations
The DSX-1 specification defines a particular pulse shape that guarantees an allowable power spectral
density at the DSX-1 cross-connect point. By using the power requirements of this pulse shape and the
known dB loss for the permitted cable types, a maximum cable distance (from a DS1 circuit pack to a
DSX-1 cross-connect point) may be determined. For either building wiring or shielded cable (the two
cable types approved for DS1/DMI/ISDN-PRI interconnections), maximum distance between the
DS1/DMI/ISDN-PRI and a DSX-1 cross-connect point is 655 feet. If transmission terminal equipment
not providing a DSX-1 is used, this maximum distance may be different. When applicable, refer to the
installation manuals for the appropriate terminal equipment.
Network Channel Terminating Equipment (NCTE)
The Network Channel Terminating Equipment (NCTE), also called a channel service unit (CSU), is
considered customer-premises equipment and is always required when connecting to network-provided
metallic transmission facilities. NCTEs may also be required on some customer premises applications.
For example, if the on-site distance between the two endpoints is such that office repeaters or line
repeaters are required, then NCTEs or their equivalent must be used. NCTEs are generally not required
when nonmetallic facilities such as fiber and microwave are used.½
Features provided by most NCTEs include:
lOffering bipolar signaling, return-to-zero operation, balanced-to-ground design, zero DC component
on signal outputs, DSX-1 between the customer’s terminal equipment, and a 1.544M-bps digital data
rate
lMonitoring of the input DS1 or, when necessary, adding pulses (1s) to ensure that the ones-density
requirements are met
ADDENDUM 1 (December 1990) to 555-025-101, Issue 4 
						

							DS1 TRANSMISSION AND CABLING3-3
l
l
l
l
l
lRemoving bipolar violations (which implies incompatibility with B8ZS line coding)
Termination of a DS1 or regeneration of received data using an office repeater
Provisions for supplying DC power to a DS1 to power line repeaters
A fault-locating jack to aid in testing repeaters on DS1s
Jacks for manually looping the NCTE and aiding in maintenance testing
A DC-triggered remote (toward the far end) loopback relay½
Other optional features include inband loopback control and the ability to pass bipolar violations. The
most frequently used NCTEs are the 551V and the 551V ST. Other vendor-provided NCTEs may have
distance limitations different from those for the 551V and 551V ST.
NOTE: The 551V has a maximum transmit distance (toward a Generic 1 or Generic 2) of 85 feet.
Therefore, when this type of NCTE (the 55lV) is used, the DS1 should be optioned or administered
accordingly. The 551V ST has a maximum transmit distance (toward a Generic 1 or Generic 2) of
655 feet. Exact distance settings are usually determined at installation time and by configuring the
NCTEs user-selectable option switches. Switch option selection must be coordinated with the
particular switch DS1.½
½
For most types of NCTEs the critical circuitry (such as, network protection and ones-density
enforcement) are normally line-powered from the CO using a 60-mA current loop. If power from the
CO is not available, then power must be provided locally. The type of power required (120 VAC or
–48 VDC) generally depends on installation/engineering specifications and on the NCTE being used;
refer to the installation and/or user’s manuals for the particular NCTE. The NCTE’s noncritical circuits
(such as, error monitoring, alarming) are always powered locally.½
½
The following six tables describe DIP-switch settings for ESF T1 Standalone and ESF T1 Multiline
NTCEs. The DIP-switch settings apply to configurations shown in figure 3-1, NCTE Framing
Configurations. The legend for tables 3-1 through 3-6 is given next.
NOTE: If a switch is reset, you must power down the NCTE before the change will go into effect.
LEGEND
OOpen/Off/Up
DfltFactory Default
C
Closed/On/DownNANot Used½
½
½
½
½
½
½
ADDENDUM 1 (December 1990) to 555-025-101, Issue 4 
						

							3-4DS1 TRANSMISSION AND CABLING
TABLE 3-1. CSU #1 and Bit Error Rate Threshold Switch Settings½
½
ESF T1 NCTE
Standalone½
D4 3Switch
NumberESF T1 NCTE
Multiline
DIP-
Switch
Switch
Name
NumberDfltESF 1ESF 2ESF 1ESF 2D4 3
/D4
SW5isDflt
SW4isDflt
NANA
NANANA
NANANA
NA
Dflt
 /D4
C
C
C
C
C
C
C
O SW1-1
SW1-2
SW1-3
SW1-4
SW1-5
SW1-6
SW1-7
SW1-8SW5-1
SW5-2
SW5-3
SW5-4
SW5-5
SW5-6
SW5-7
SW5-8 O
C
C
C
C
SW1
C
C
C
O
C
OSW2
O
O
NAONAONAO NCTE
#1Dflt
is
SW4-1
SW4-2
SW4-3
SW4-4
SW4-5
SW4-6
SW4-7
SW4-8O
C
O
O
O
O
O
O SW2-1
BitSW2-2
ErrorSW2-3
SW2-4isDflt
Rate
SW2-5
ThreshSW2-6
SW2-7
SW2-8NA
NA
NANA
NA
NA
NOTES:
1.
2.
3.ESF means ESF framing from end-to-end (see Configurations A and D in figure 3-1)
ESF/D4 means ESF framing over the span with D4 framing to the switch (see Configurations B and E in figure 3-1)½
½
½
½
½
D4 means D4 framing from end-to-end (see Configurations C and F in figure 3-1)
TABLE 3-2. FS and ES Threshold Switch Settings
DIP-
Switch
NameESF T1 NCTEESF T1 NCTE
Multiline
Standalone
Switch
NumberDfltESF 
1ESF 2D4 3SwitchNumber
DfltESF 1ESF 2D4 3
/D4
/D4
SW3-1
SW3-2
SW3-3
SW3-4O
O
O
OSW3-1
SW3-2
SW3-3
SW3-4O
O
O
O
FS
ThreshSW3
isNASW3
isNA
SW3-5
SW3-6
SW3-7
SW3-8O
O
O
OSW3-5
SW3-6
SW3-7
SW3-8O
O
O
O
SW4-1
SW4-2
SW4-3
SW4-4C
C
C
C
NA
NA
NA
NANA
NA
NA
NANA
NA
NA
NASW2-1
SW2-2
SW2-3
SW2-4O
O
O
O
ESThreshSW2
isNASW4-5
SW4-6
SW4-7
SW4-8C
C
C
CNA
NANA
NANA
NASW2-5
SW2-6
SW2-7
SW2-8 O
CO
O
O
O O
CO
C
NOTES:
1.
2.
3.ESF means ESF framing from end-to-end (see Configurations A and D in figure 3-1)
ESF/D4 means ESF framing over the span with D4 framing to the switch (see Configurations B and E in figure 3-1)
D4 means D4 framing from end-to-end (see Configurations C and F in figure 3-1)½
½
½
½
ADDENDUM 1 (December 1990) to 555-025-101, Issue 4 
						

							DS1 TRANSMISSION AND CABLING3-5
TABLE 3-3. Configuration A and B Switch Settings½
DIP-
Switch
NameESF T1 NCTEESF T1 NCTE
StandaloneMultiline
Switch
NumberDfltESF 
1ESF 2
/D4D4 
3Switch
NumberDfltESF 1ESF 2
/D4D4 
3
SW5-1
SW5-2
SW5-3
SW5-4C
C 4
C 5
OO
C
C
CC
C
C
OC
C
C
OSW1-1
SW1-2
SW1-3
SW1-4O
O
O
ONANANA
O
O
CO
O
OO
O
O
Config
B
SW5-5
SW5-6
SW5-7
SW5-8O
O
O
OC
O
O
NAO
O
O
NAO
O
OSW1-5
SW1-6
SW1-7
SW1-8O
C 6
C 7
CC
C
C
OO
C
C
CO
C
C
C
NA
SW6-1
SW6-2
SW6-3
SW6-4C 
8
O 5
O 4
CO
O
O
CO
O
O
CO
O
O
CSW7-1
SW7-2
SW7-3
SW7-4O 
9
O 6
O 7
CO
O
O
CO
O
O
CO
O
O
C
Config
CC
CC
ASW6-5
SW6-6
SW6-7
SW6-8C
O
O
C 
8
C
NA
NA
CCNA
NA
CNA
NASW7-5
SW7-6
SW7-7
SW7-8C
O
O
O 9
NA
NANA
NANA
NA
CO
OO
NOTES:
1.
2.
3.
4.
5.ESF means ESF framing from end-to-end (see Configurations A and D in figure 3-1)½
½
½
½
ESF/D4 means ESF framing over the span with D4 framing to the switch (see Configurations B and E in figure 3-1)
D4 means D4 framing from end-to-end (see Configurations C and F in figure 3-1)
If the span uses ZCS (AMI) line coding, then SW5-2 = C and SW6-3 = O
If the span uses B8ZS line coding, then SW5-2 = O and SW6-3 = C
If the switch uses ZCS (AMI) line coding, then SW5-3 = C and SW6-2 = O
If the switch uses B8ZS line coding, then SW5-3 = O and SW6-2 = C
6.
7.
8.If the span uses ZCS (AMI) line coding, then SW1-7 = C and SW7-3 = O
If the span uses B8ZS line coding, then SW1-7 = O and SW7-3 = C½
½
½
½
½
If the far-end of the span is a 4ESS, then SW6-1 = C and SW6-8 = O
If far-end of the span is a switch, then SW6-1 = O and SW6-8 = C
If the far-end of of the span is a 4ESS, then SW7-1 = C and SW7-8 = C
If far-end of the span is a switch, then SW7-1 = O and SW7-8 = O
TABLE 3-4. Equalizer Switch Settings½
ESF T1 NCTE ESF T1 NCTE
Standalone DIP-
Switch
NameMultiline
501’
to
655’
NA
O
O
O
O
C
C
C 151’
to
450’
O
C
O
C
O
C
O
ODflt0’
to
285 ’286’
to
500’ Switch
Number
Dflt0’
to
150’451’
to
655’
Switch
Number
SW7-1
SW7-2
SW7-3
SW7-4
SW7-5
SW7-6
SW7-7
SW7-8C
O
O
O
O
O
O
OC
O
O
O
O
O
O
OSW6-1
SW6-2
SW6-3
SW6-4
SW6-5
SW6-6
SW6-7
SW6-8 O
O
O
O
C
O
C
NA
O
O
O
O
O
C
C
CNAO
O
C
C
C
C
ONAO
O
O
O
C
C
C Equa-
lizer
NOTE: The distance should be measured when the NCTE is not adjacent to the switch.
ADDENDUM 1 (December 1990) to 555-025-101, Issue 4½ 
						

							3-6DS1 TRANSMISSION AND CABLING
TABLE 3-5. PWR Switch Settings½
ESF T1 NCTE
DIP-
Switch
NameESF T1 NCTE
Standalone
Multiline
Switch
NumberDfltPos.Pos.Pos.
Switch
NumberDfltPos.Pos.
Pos.
#1#2#3
#1#2#3
PWRS1
DL
DL
local
power
WETWL
local
power
DRY
SP
SPAN
power
S1
DL
DL
local
power
WETWL
local
power
DRYSP
SPAN
power
NOTE: Local exchange companies (LECs) are currently installing Smart jacks requiring the use of a 0dB line build-out network (LBO).½
½
½
½
½
TABLE 3-6. XMT (LBO) Switch Settings½
DIP-ESF T1 NCTEESF T1 NCTE
Standalone
SwitchMultiline
NameSwitchDfltPos.
Pos.Pos.SwitchDfltPos.Pos.
Number#1#2
#3Number#1#2Pos.#3
XMT
(LBO)S20dB0dB
7.5dB15dBS27.5dB0dB7.5dB15dB½
½
½
NOTE: LECs are currently installing Smart jacks which require the use of a 0dB LBO.½
CONFIG-
URATIONSWITCH
FRAMINGSPANFRAMINGSWITCH
FRAMING½
A
B
C
D
E
FGENERIC 1
GENERIC 1
GENERIC 1
GENERIC 1
GENERIC 1
GENERIC 1ESF
D4
D4
ESF
D4
D4NCTE
NCTE
NCTE
NCTE
NCTE
NCTEESF
ESF
D4
ESF
ESF
D4
NCTE
NCTE
NCTE
NCTE
NCTE
NCTEESF
D4
D4
ESF
D4
D4
GENERIC 1
GENERIC 1
GENERIC 1
SYSTEM 85
SYSTEM 85
SYSTEM 85½
½
½
½
½
½
½
Figure 3-1. NCTE Framing Configurations½
On-Premises Cabling
When both endpoints are in the same building, cabling has three distance ranges and the required
equipment depends on the range. It is assumed that all cabling remains inside and is not exposed to
foreign potentials such as lightning and needs no appropriate protection. Since all equipment is on
customer premises, the customer is responsible for maintaining the equipment. Figure 3-2, On-Premises
Metallic-Cable Configurations, shows the various possible on-premises metallic cabling configurations.½
½
½
½
ADDENDUM 1 (December 1990) to 555-025-101, Issue 4