PHS MoU Document
B-IW3.00-02-TS
Title: Public Personal Handy-Phone System : Network Interworking
between a Public PHS network and a Public Switched Telephone
Network (PSTN)
Version: 02
Date: July 31, 1998
PHS MoU Classification: Unrestricted
List of contents:

1. Introduction
2. Scope
3. Interworking configuration and network characteristics
4. Public PHS network bearer services suitable for public PHS networkPSTN interworking
5. Connection type suitable for public PHS network-PSTN interworking
6. Functional requirements for public PHS network-PSTN interworking
Annex A Glossary and Abbreviations

Number of pages: 12

PHS MoU Group
c/o Association of Radio Industries and Businesses (ARIB)
14F, Nittochi Bldg., 4-1, Kasumigaseki 1-choume, Chiyoda-ku, Tokyo 100, Japan
TEL +81-3-5510-8599 FAX +81-3-3592-1103© PHS MoU Group1998

PHS MoU Document
B-IW3.00-02-TS
VersionHistory of Revised Versions
Date
Outline01

Dec. 19, 1997 Established

02

July 31, 1998

64 kbit/s unrestricted data bearer service is
addedB-IW3.00-02-TS

Public Personal Handy-Phone System:
Interworking Between a Public PHS network anda Public Switched Telephone Network (PSTN)< Summary >1. Relationship with International Standards
This specification specifies network interworking between a public PHS network and a public
switched telephone network based on ITU-T Recommendation I.530 which specifies ISDN-PSTN
interworking arrangements.
2. Differences to/from International Recommendations(1) Network model and terminology
ITU-T Recommendation I.530 specifies interworking where interworking networks are ISDN and
PSTN. This specification changes this model to specify interworkig between a public PHS network
and a PSTN. The differences of model and terminology from ITU-T Recommendation I.530 are
summarized in Table Summary-1/B-IW3.00.
(2) Specifications
The differences of specifications from ITU-T Recommendation I.530 are summarized in Table
Summary-2/B-IW3.00.
The following specifications have been deleted from ITU-T Recommendation I.530:- Packet mode interworking;- Multi-use information transfer;
3. Reference
ITU-T Recommendation : I.5xx series
PHS MoU Documents : B-IF2.xx, B-IF3.xx, B-Ifx.xx series
4. Item for Further Study
None

B-IW3.00-02-TS(1)

Table Summary-1/B-IW3.00 Differences of model and Terminology from ITU-T
Recommendation I.530
Item
I.530
This specifications
Interworking network Interworking networks are ISDN and Interworking networks are public PHS
model
PSTN.
network and PSTN.
Network configuration Networks are ISDN and PSTN.
Networks are public PHS natwork andfigurePSTN
Terminology
ISDN – in a context of service
public PHS network
64kbit/s unrestricted
32kbit/s unrestricted and 64kbit/s
unrestricted
ISDN user
public PS
Kx
IF3 (Kx)
Reference
ITU-T Recommendations
PHS MoU Documents
Q.699
B-IW1.02
Q.931
B-IF2.02
Q.761
B-IF3.31
Q.762
B-IF3.32
Q.763
B-IF3.33
Q.764
B-IF3.34
I.520
B-IW2.00
I.441
B-IF2.03
I.451
B-IF2.02(2) B-IW3.00-02-TS

Table Summary-2/B-IW3.00 Differences of specifications from ITU-T Recommendation I.530
SectionDifferences
5. Public PHS network bearer services suitable for -Descriptions including Table/I.530 relating to
public PHS network – PSTN interworking
packet mode are deleted.
-Description relating to multi-use are deleted.
5.1 Public PHS network bearer services suitable for -Description relating to multi-use are deleted.
public PHS network to PSTN interworking(circuit)
5.3 Public PHS network bearer service suitable for -This section relating to packet mode is not
public PHS network to PSTN interworking
included(packet)5.4 Public PHS network bearer service suitable for -This section relating to packet mode is not
PSTN to public PHS network interworking
included.
(packet)6. Connection type suitable for public PHS-Descriptions including Table2/I.530 relating to
network-PSTN interworking
packet mode are detected.
6.5 Control of speech processing and echo control -Description relating to multi-use are deleted.
devices
7.6 A/• law encoding-Description relating to multi-use are deleted.
8. Handling of packet mode calls between public -This section relating to packet mode is not
PSH network and PSTN subscribers
included.
Annex A GLOSSARY and ABBREVIATIONS-Annex A is added.

B-IW3.00-02-TS(3)

B-IW3.00-02-TS
Public Personal Handy-Phone System:
Network Interworking between a Public PHS network anda Public Switched Telephone Network (PSTN)

Contents

1. General ................................................................................................................................................

1

2. Scope ...................................................................................................................................................

1

3. Interworking configuration and network characteristics ....................................................................

1

3.1 Interworking configurations........................................................................................................

1

3.2 Key public PHS network and PSTN characteristics and related interworking functions...........

2

4. Public PHS network bearer services suitable for public PHS network-PSTN interworking .............

2

4.1 Public PHS network bearer services suitable for public PHS network to PSTN
interworking (circuit) ....................................................................................................................

3

4.2 Public PHS network bearer services suitable for PSTN to public PHS network
interworking (circuit) ....................................................................................................................

4

5. Connection type suitable for public PHS network-PSTN interworking ............................................

4

6. Functional requirements for public PHS network-PSTN interworking ..............................................

5

6.1 Interworking between signalling systems...................................................................................

5

6.2 Provision of interworking indications.........................................................................................

6

6.3 Generation of in-band tones and announcements .......................................................................

7

6.4 Handling of non-voice calls between public PHS network and PSTN subscribers....................

9

6.5 Control of speech processing and echo control devices .............................................................

10

6.6 A/P law encoding ........................................................................................................................

10

Annex A GLOSSARY and ABBREVIATIONS ............................................................................

11

B-IW3.00-02-TSi

1. GeneralIn many countries, digitization of the existing PSTN has been ongoing over a number of years throughthe implementation of digital switching and transmission facilities.
However, it is foreseen that digitization will be a long transition period for some networks. Thus, thepublic PHS network using existing ISDN is necessary to introduce of interconnecting between
existing PSTN and existing ISDN.
The purpose of this document is to identify the interworking funcitons and requirements to support
interworking between a public PHS network and a PSTN.
2. Scope
The purpose of this document is to describe the general arrangements for interworking between apublic PHS network and a PSTN. Both the provision of public PHS network voice transmission anddata transmission services are within the scope of this document.
3. Interworking configuration and network characteristics
3.1 Interworking configuraitons
See Figure 3-1/B-IW3.00.
IF3(Kx)
Public PHS network

PSTN
user

PSTN

Public PSa) Interexchange scenario

PSTN
user

Public PHS network/PSTN
Public PSb) Intra-exchange scenario

NOTES
1. In part a) refer to PHS MoU document B-IW0.01 for the definition of IF3(Kx) reference point.
2. Part b) illustrates the case where no clear division exists between public PHS network and PSTN network
components.

Figure 3-1/B-IW3.00 Interworking configurations

B-IW3.00-02-TS 1

3.2 Key public PHS network and PSTN characteristics and related interworking functions
Table 4-1/B-IW3.00 identifies the key characteristics of a public PHS network and a PSTN, indicating
possible interworking functions to accommodate dissimilar characteristics.
3.2.1 Location of interworking functions
Given that the transition period from a PSTN to an ISDN may occur over a long period of time, there
will be an ongoing requirement for public PHS network-PSTN interworking. In such a situation, it islikely that interworking functions will be required at not just one but several locations. As thetransition to ISDN continues, interworking points will come into existence and later may not be
required.
Points where interworking may exist are-within the local exchange;-at transit exchange;-

at international gateway offices.

NOTE – The optimum location of each interworking function may be specific per interworking
function and dependent on the usage of the service, network topology, etc.
4. Public PHS network bearer services suitable for public PHS network-PSTN interworking
This clause considers the subject of public PHS network services suitable for public PHS networkPSTN interworking. The discussions dealing with the public PHS network to/from PSTN direction are
addressed in individual subclasses, as is the subject of circuit mode.

2

B-IW3.00-02-TS

Table 4-1/B-IW3.00 Key public PHS network and PSTN characteristics
Public PHS network

PSTN

Interworking
functions

Subscriber interface

DigitalAnaloguea

User network signallingOut-bandMainly in-band (e.g. DTMF)b, ec(B-IF2.03, B-IF2.02)
User terminal equipment

Digital TE (public PHS

Analogue TE (e.g. dial pulse

supported

network NT,TE1 or TE2 +telephones, PABXs, modem-TA)equipment DTEs)

SS No. 7 ISDN user partIn-band (e.g. R1, R2 or; No.

(ISUP)

4, No. 5) or out-band

Interexchange signallingd, e(e.g. SS No. 6, SS No. 7
TUP)
Transmission facilities

DigitalAnalogue/digitala

Information transfer mode

CircuitCircuitfInformation transfer

Speech, digital unrestricted,

3.1 kHz audiofCapability

3.1 kHz audio, etc.

(voice/voice-band data)

Interworking functions
a. Analogue-to-digital and digital-to-analogue conversion on transmission facilities.
b. Mapping between PSTN signals in the subscriber access and B-IF2.02 message for intra-exchange calls.
c. Support of communication between modem-equipped PSTN DTEs and public PHS network terminals.
d. Conversion between the PSTN signalling system and Signaling System No. 7 ISDN user part.
e. Mapping between signals in the public PHS network subscriber (B-IF2.03, B-IF2.02) access and PSTN in-band
interexchange signalling (e.g. R1).
f.

Further study required.

4.1 Public PHS network bearer services suitable for public PHS network to PSTN interworking(circuit)
Currently, there are three identified bearer services that could be used within the public PHS network
for public PHS network to PSTN interworking. These are (refer to Recommendation I.231)i)circuit mode 64 kbit/s, 8 kHz structured bearer services, usable for speech informationtransfer (Note 1);ii) circuit-mode 64 kbit/s, 8 kHz structured bearer services, usable for 3.1 kHz audio
information transfer (Note 2);iii) circuit-mode 64 kbit/s unrestricted, 8 kHz structured bearer service (Note 3).

It is recognized that the communication characteristics obtained for each of these three bearer services
on a public PHS network to PSTN basis may not be the same as that obtained for public PHS network
to public PHS network configurations/NOTES
1 This bearer service is used for the public PHS network to PSTN-interworking for the purpose of speech

B-IW3.00-02-TS 3

2

3

4

information transfer.
This bearer service is used for the public PHS network to PSTN interworking for the purpose of 3.1 kHz
audio information transfer. For PSTN to public PHS network interworking, this bearer service will beselected at the boundary of the PSTN to the public PHS network for the purpose of speech informationtransfer and for 3.1 kHz audio information transfer.
This bearer service may be required for public PHS network PSTN interworking. Refer to Recommendation
I.231 for the 64 kbit/s interworking service requirements. If 32 kbit/s unrestricted bearer is selected, the userrate and intermediate rate shall be less than or equal to 32 kbit/s.
Public PHS network-PSTN interworking means interworking both ways between public PHS network and
PSTN, while public PHS network to PSTN refers to a call initiated in the public PHS network andterminated in the PSTN, and PSTN to public PHS network refers to a call initiated in the PSTN andterminated in public PHS network.

4.2 Public PHS network bearer services suitable for PSTN to public PHS network interworking(circuit)
Currently, there is no internationally recognized method of service differentiation between voice andnon-voice calls originating in the PSTN. However, the “ciruit-mode 64 kbit/s, 8 kHz structured bearer
service for 3.1 kHz audio information transfer” provides for the capability equivalent to PSTN. (seerecommendation I.231.) Therefore, PSTN calls may interwork to this service in public PHS network.
The call progress indicator within ISUP will identify when interworking between public PHS network
and PSTN occurs. This indicator will enable the public PHS network to select a connection thatwould support 3.1 kHz audio. A V-Series terminal connected to the public PHS network via aterminal adaptor and using the 32 kbit/s unrestricted or 64 kbit/s unrestricted bearer service requires
the use of an IWF (including a modem) for calls from PSTN users. To effect the connection, a 64
kbit/s connection to the IWF would need to be used.
5. Connection type suitable for public PHS network-PSTN interworking
This clause identifies the mapping of public PHS network bearer services and possible connection
types for public PHS network-PSTN interworking. Depending on the specific public PHS network
bearer service being considered, more than one public PHS network connection type may be
applicable. However, in some cases the connection type may not be fully compatible with therequested bearer service, thereby leading to downgrading of service.
The public PHS network bearer services and possible connection types that may be used aresummarized in Table 5-1/B-IW3.00, under the four possible interworking cases. Refer to
Recommendation I.335 for more details regarding the mapping between public PHS network bearer
services and public PHS network connection types.

4

B-IW3.00-02-TS

Table 5-1/B-IW3.00ý ý Public PHS network bearer services and connection types suitable for
Public PHS network-PSTN interworking
Public PHS network conneciton types

Public PHS network
Interworking

bearer services

64 kbit/scategories

unrestricted

Speech3.1 kHz audio

32 kbit/s unrestricted

Y

N

N

Public PHS network

64 kbit/s unrestricted

Y

N

N

to PSTN (circuit)

SpeechR(1)YY

3.1 kHz audio

R(1)

N

Y

32 kbit/s unrestricted

Y

N

N

64 kbit/s unrestricted

Y

N

N

3.1 kHz audio

R(1)

N

Y

PSTN to public PHS
network (circuit)

Y: Yes Can be used (some interworking scenarios may require further study).
N: No Cannot be used.
R(1) Can be used except when A/• -law conversion and/or echo control may be required.
NOTES
1.

It is recognized that existing PSTN services must be supported by public PHS network using currently defined public
PHS network bearer services.

2.

It is possible that the service obtained on each of the bearer services for public PHS network to PSTN interworking may
not be the same as that obtained for public PHS network to public PHS network configurations.

3.

Refer to Recommendation I.231 for the service requirements for 64 kbit/s interworking. Various mechanisms for public
PHS network-PSTN interworking supporting V-Series terminals connected to the public PHS network using the 32
kbit/s unrestricted or 64 kbit/s unrestricted bearer service are contained in Recommendation I.515. Procedures require
further study.

4.

Other public PHS network bearer services and connection types that may be applicable for public PHS network-PSTN
interworking are for further study.

6. Functional requirements for public PHS network-PSTN interworking
6.1 Interworking between signalling systems
Interworking between signalling systems, specifically for interexchange calls between the PSTN
signalling system (which may be in-band) and Signaling System No. 7 (ISDN UP) on a public PHS
network, may be required. The interworking procedures are specified in PHS MoU Document BIW1.02.
For intra-exchange calls between the public PHS network and PSTN subscriber, interworking
between B-IF2.02 messages and signals in the PSTN subscriber access may also be required.

B-IW3.00-02-TS 5

6.2 Provision of interworking indications
An interworking indicaiton is required for the public PHS network local exchange (LE) to know thatpublic PHS network-PSTN interworking has occurred. ISUP B-IF3.31 – B-IF3.34 and B-IF2.02
protocols have the ability to identify this interworking situation to the public PHS network LE and the
public PHS network terminal (call progress indicator).
The public PHS network terminal would be informed in every case that public PHS network
interworking has occurred. This information is required to satisfy as a minimum the requirement to:--tell the terminal to connect the B-channel so that in-band tones and announcements can bereceived when public PHS network-to-PSTN calls are originated;tell the public PHS network terminal that some or all of service selection information andaddress may be unavailable – the terminal may then be required to accept the call without outband compatibility checking;tell data terminal equipment to anticipate in-band handshaking signals for public PHS network
calls.

The following interworking scenarios have been recognized:a) a public PHS network-PSTN call which uses a Signaling System No. 7 ISUP connection
between the originating and terminating local exchanges;b) a public PHS network-PSTN call which uses a non-Signaling System No. 7 ISUP connection(e.g. R1, Signaling System No. 7 TUP) between the originating and terminating local
exchanges;c) a public PHS network-PSTN call which involves a combination of Signaling System No. 7
ISUP and non-Signaling System No. 7 ISUP interexchange signalling connections between theoriginating and terminating local exchanges;d) a public PHS network-PSTN call within the same local exchange (i.e. no interexchange
signalling).
6.2.1 Network indication of modification of communication characteristics
The network will always provide an indication to the user of modification of communication
characteristics. The modification of communication characteristics may be due to the following
reasons:-

interworking with another network;
resource constraints in the network

In addition to providing an indication, the network may solicit user acceptance of the modification ofcommunication characteristics in certain cases. Examples are:-downgrading of service;
upgrading of service.

For most interworking cases, user acceptance is not applicable.

6

B-IW3.00-02-TS

There may be a requirement for the resolution of information transfer capability requests other thanspeech and 3.1 kHz audio on public PHS network-to-PSTN calls. The choices of rejection (which a
suitable cause indication) or negotiation (involving parameter exchange) are possible(Recommendation I.515).
There may also be requirement for the rejection of supplementary service requests available on an
public PHS network, but not supported on the PSTN. However, negotiation for supplementary
services may be possible as well.
The principles for call negotiation in an public PHS network-PSTN interworking situation are forfurther study.
6.2.2 Failure indication
Failure indication, when carried by the B-IF2.02 and ISUP signalling messages, should be meaningful
and give a clear indication of the reason.
The network failure indication should be able to identify the network where congestion occurred. Thismay be of user in networks allowing ROA selection.
6.3 Generation of in-band tones and announcements
In-band tones and announcements are provided for all speech and 3.1 kHz audio bearer service calls
between an public PHS network and a PSTN (reference Recommendation E.180. Within public PHS
network, in-band tones and announcements, with the exception of ring-back tone, should be provided
at a point as close as possible to the calling user (i.e. network, PABX, or terminal). Wheneverpossible, out-band messages should also be used within the public PHS network and the local access.
The network (Public PHS network or PSTN) must be capable of generating in-band tones andannouncements. However, for public PHS network-to-PSTN interworking cases, the public PHS
network terminals will receive the in-band tones and announcements whenever the tones are
generated within the PSTN, i.e. beyond the interworking point. Nevertheless, this does not preclude
the terminal from providing its own tones and announcements.
In-band ring-back tone should be generated by the terminating exchange (or terminating PABX).
Furthermore, two call scenarios exist:a) the call is unsuccessful (user busy, network congestion, etc.);b) the call is delivered successfully.
Regardless of the call type, the same in-band tones and announcements (depending on the callscenario) should be provided to the calling user.

B-IW3.00-02-TS 7

6.3.1 Call type 1: PSTN-to-public PHS network
6.3.1.1 Unsuccessful call delivery
When the point of call failure (i.e. the point at which the call cannot proceed further) is within the
PSTN or at the PSTN user, normal PSTN procedures apply.
When the point of call failure is within the public PHS network or at the public PS, the public PHS
network should send the appropriate out-band clearing message as far back towards the gateway
exchange as possible.
--

If the out-band message can be sent all the way through to the gateway exchange, then thegateway exchange should pass the information to the PSTN using the PSTN’s normal
procedures (i.e. out-band if the PSTN supports the out-band message, otherwise in-band).
If the message cannot be sent out-band all the way to the gateway exchange, then theappropriate in-band tone or announcement should be provided by the public PHS network at
the point where out-band signalling is no longer capable of handling the message.

For the above cases, the clearing message should not be sent prior to the completion of theannouncement.
6.3.1.2 Successful call delivery
If the call is delivered successfully to the public PS, then the terminating public PHS network
exchange should generate in-band ring-back tone towards the PSTN user.
6.3.2 Call type 2: Public PHS network-to-PSTN
6.3.2.1 Unsuccessful call delivery
When the point of call failure is within the public PHS network, the call should be handled as a public
PHS network-to-public PHS network call (see PHS MoU Document B-IW2.00).
When the point of call failure is within the PSTN, the PSTN’s procedures apply. For instance, if the
PSTN supports out-band signalling to the gateway exchange, then the gateway exchange should map
the message to the appropriate out-band public PHS network clearing message (i.e. the gateway
exchange handles the call as a public PHS network-to-public PHS network call). If the PSTN does notsupport out-band signalling, then it will generate the appropriate in-band tone or announcement.
The public PHS network terminal should be alerted to the fact that interworking has occurred so thatthe user can be prepared to receive the appropriate in-band tone or announcement. The intermediate
interworking point will provide the interworking message which will suppress, when necessary, tone
generation in the public PHS network terminal, and pass through any in-band tones.
For the above cases, the clearing message should not be sent prior to the completion of theannouncement.

8

B-IW3.00-02-TS

6.3.2.2 Successful call delivery
If the call is delivered successfully to the PSTN user, then the terminating PSTN exchange will
provide in-band ring-back tone. The public PHS network terminal should be alerted to the fact thatinterworking has occurred so the user can be prepared to receive the in-band ring-back tone.
6.4 Handling of non-voice calls between public PHS network and PSTN subscribers
There may be an interworking requirement for the capability to interconnect modem-equipped
terminals on the PSTN and compatible terminals on a public PHS network access. This may in the
future include a means for compatibility checking and the provision of a modem pool to perform A/Dconversion and rate adaptation (Recommendation I.515)
There are in principle two alternative approaches to provide data communication between a public
PHS network customer and a PSTN customer:i)

The data terminal of the public PHS network customer is connected to a modem which inturn is connected to an A/D converter (PCM). A call will be handled as for telephony.
Further study is required to determine what interworking functions are required in this case.
ii) The data terminal of the public PHS network customer is connected to a public PS, i.e. thedata flow is rate adapted to 64 kbit/s. At a suitable interworking point, the original data flow
(e.g. 1.2 kbit/s) is extracted and converted to “analogue” form by a modem for furthertransfer to the remote data terminal (i.e. the usage of modem pools). Mechanisms formodem interworking are contained in Recommendation I.515.

To handle non-voice calls in a public PHS network-PSTN interworking situation, the followinginterworking functions may be required.
a) capability to distinguish a data call and its relevant parameters when the call is coming froma PSTN;b) capability to distinguish a data call and its relevant parameters when the call is going to a
PSTN;c) special routing algorithms for inclusion of proper IWFs as detected in a) and b);d) IWFs for protocol conversion as detected in a) and b).
For interworking between public PHS network and PSTN, the need for in-band parameter exchange isrecognized as necessary, with the understanding that out-band parameter exchange should be usedwhenever possible (refer to Recommendation I.515).
NOTE – When public PHS network-PSTN interworking, using a modem pool in conjunction with the 32 kbit/s
unrestricted or 64 kbit/s unrestricted bearer service, it may not be possible to extend PSTN supervisory
tones to the public PS. The interworking implications of this in the public PHS network are for further
study.

B-IW3.00-02-TS 9

6.5 Control of speech processing and echo control devices
Connections provided for public PHS network/PSTN interworking may use speech processing
techniques as long as these do not restrict the required information transfer. Restrictive devices should
be functionally modified or removed using, for example, the 2.1 kHz in-band [ECD (echo control
device) disabling] tone.
Digital circuit multiplication equipment (DCME) for example is designed to be compatible with the
3.1 kHz audio transfer capability. Echo control devices and their use in the PSTN are recommended in
Recommendation G.131.
Similar Recommendations should apply to the public PHS network/PSTN interworking case. In
particular, both echo suppressers and echo chancellors must be located within a range limitation of the
four-wire/two-wire interface. These limits are mentioned in 2.2/G131, 1.1.3/G164 and 3.2/G.165. If
echo control devices are included in the public PHS network connection, they will need to have thecapability of being disabled by the 2.1kHz echo control disabling tone generated by modems as is thecurrent practice in the PSTN. While echo suppressers should respond to a 2100 Hz tone
(Recommendation G.164), echo chancellors should only respond if the tone includes phase reversals
as specified in Recommendation G.165. It is recommended that the 2.1 kHz tone should not be
converted into a public PHS network signalling message and vice-versa.
6.6 A/P
P law encoding
The treatment of A/P law encoding and translation in public PHS network/PSTN interworking can bebased on the continuation of existing procedures whereby appropriate A/P law translation is
performed by the P-law network when crossing international boundaries. Terminals would encode
speech and 3.1 kHz audio using the G.711 law appropriate to the resident network. Unrestricted 32
kbit/s or unrestricted 64 kbit/s services bit streams would not be manipulated in any way by the public
PHS network: terminals would be free to use any encoding (including G.711 or G721) as deemed
appropriate between themselves when unrestricted 32 kbit/s or unrestricted 64 kbit/s capability isrequested.

10

B-IW3.00-02-TS

AnnexA GLOSSARY and ABBREVIATIONSThis annex forms an integral part of this document
GLOSSARY***A******B******C******D******E******F******G******H******I***
IF3(Kx)PHS MoU
The network interworking reference point is the IF3(Kx) reference point when the network directlyinterconnected to the public PHS network is a non-ISDN***J******K******L******M******N******O******P******Q******R******S******T******U******V******W******X******Y******Z***

B-IW3.00-02-TS 11

ABBREVIATIONS
DCME
DTE
DTMF
IDN
ISDN
ISUP
IWF
LE
NT
PABX
PCM
PSTN
SS No.7
TE
TA
TUP

12

Digital circuit multiplication equipment
Data terminal equipment
Dual-tone multi-frequency
Integrated digital network
Integrated Service Digital Network
ISDN user part
Interworking function
Local exchange
Network termination
Private Automatic Branch Exchange
Pulse code modulation
Public switched telephone network
Signaling System No. 7
Terminal equipment
Terminal adaptor
Telephone user part.

B-IW3.00-02-TS

ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T
ITU-T