SIST I-ETS 300 245-4 E1:2003

• Abstract:

  To specify an interface for additional equipment to an ISDN telephony terminal.

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.080 - Integrated Services Digital Network (ISDN)
• Technical Committee: SS EIT - Technical Board for the electrotechnical, information technology and telecommunications fields
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Dec-2003
• Due Date: 01-Dec-2003
• Completion Date: 01-Dec-2003
• Ref Project: ETSI I-ETS 300 245-4 ed.1 (1995-02) - Integrated Services Digital Network (ISDN); Technical characteristics of telephony terminals; Part 4: Additional Equipment Interface (AEI)

SIST I-ETS 300 245-4 E1:2003 is the Slovenian adoption of ETSI’s Interim European Telecommunication Standard for the Additional Equipment Interface (AEI) of ISDN telephony terminals. It specifies the physical, electrical, logical and functional characteristics of interfaces between an ISDN telephony terminal and additional equipment, so manufacturers and testers can design and verify compatible add-on devices.

What does SIST I-ETS 300 245-4 E1:2003 specify?

SIST I-ETS 300 245-4 E1:2003 specifies a family of interfaces for connecting additional equipment to ISDN telephony terminals. The standard covers both analogue transmission of B-channel information and digital signalling between the terminal and the additional equipment, together with the protocol behavior needed for those links.

Clause 4 explains the applications and the operating principles. Clauses 5 and 6 cover the physical and transmission requirements for the X-, Y- and Z-related interfaces. Clause 7 defines the signalling protocol on the Z interface, clause 8 defines the Y-interface protocol, and Annex A gives the conformance test principles.

In practice, the document is meant for add-ons such as loudspeaking equipment, handsfree equipment, automatic answering machines, dialling functions, alarm equipment, charging devices, speech cryptography, modem/Videotex terminals and PSTN adapters. These examples show the intended use of the interface family, not just one accessory type.

What are the key requirements of SIST I-ETS 300 245-4 E1:2003?

• The AEI is an optional extension to an ISDN telephony terminal. Clause 4 says the interface supports and extends terminal functionality, and that additional terminal software may be needed to handle the extra equipment and its application. In practice, the terminal is not just carrying speech - it also has to manage the behavior of the connected accessory.

• The standard allows one AE on the interface, with cascading limited to a maximum of three AEs. Clause 5.1 says the terminal sees only one logical and physical unit at the interface, even if several AEs are cascaded. That matters when a vendor splits functions across separate boxes, because the combined chain still has to behave as one accessory.

• The X-interface carries analogue B-channel information, while the Y-interface carries digital signalling. Clause 1 and clause 3 define the X-interface as bi-directional analogue transmission and the Y-interface as bi-directional signalling message transfer. In practice, X handles speech or other 3.1 kHz or 7 kHz audio paths, while Y handles call-related control and coordination with the AE.

• The Y-interface uses asynchronous serial transmission at 1 200 bit/s with an 11-bit frame format. Clause 8.2 fixes the layer 1 format as 1 start bit, 8 data bits, odd parity and 1 stop bit. That is important for implementers because the accessory and terminal must match the exact framing before any higher-level signalling can work.

• Clause 5 sets the physical and transmission checks for the X- and Y-side interfaces. These include relative levels, interface impedances, gain variation with input level, distortion, attenuation or frequency distortion, out-of-band signals, single-frequency noise, noise, group delay, short-circuit protection and Terminal Coupling Loss (TCL). In practice, this is the part that protects speech quality and compatibility, especially where the terminal is effectively acting as a carrier for the additional equipment.

• The Z-related interfaces cover analogue access and ON/OFF signalling, with explicit protection and safety expectations. Clause 6 describes a 2-wire Z analogue interface and a Z signalling interface for semi-permanent states such as connection requested or AE ready. It also requires short-circuit protection, protection against low voltages, and galvanic decoupling in the AE as part of the safety arrangement.

• Clause 8 defines the Y-interface as a layered protocol with layer 2 timers, layer 3 message handling and error handling. The protocol model is used to handle call establishment, call release, takeover of an existing connection, incoming calls and manufacturer-specified applications. For implementers, this means the AE must not only send bytes correctly - it must also behave correctly during call control and state changes.

• Annex A turns the requirements into conformance test principles. Annex A structures each test around purpose, test configuration, system state, stimulus, monitoring and result. That helps laboratories and quality teams check whether a terminal or accessory really meets the interface rules.

What terms does SIST I-ETS 300 245-4 E1:2003 define?

• Additional Equipment (AE): Equipment connected to an ISDN telephony terminal to provide extra functions beyond the base terminal.
• Additional Equipment Interface (AEI): The interface used to connect the AE to the terminal.
• X-interface (X-I): The analogue interface that carries bi-directional B-channel related information between the terminal and the AE.
• Y-interface (Y-I): The digital interface that carries bi-directional signalling messages between the terminal and the AE.
• Z-interface: The interface used for signalling information, including semi-permanent states and ON/OFF-type control.
• Terminal Equipment (TE): The ISDN terminal equipment side of the interface, as used throughout the protocol and test descriptions.
• dBr: A relative level referenced to the 0 dBr point at the basic user-network interface.

Who uses SIST I-ETS 300 245-4 E1:2003?

SIST I-ETS 300 245-4 E1:2003 is used by manufacturers of ISDN telephony terminals and by makers of additional equipment that plugs into those terminals. It is also used by test laboratories, certification teams and quality managers who need a common basis for conformance testing.

Design engineers use it to define the interface hardware, connectors, cable length and signalling behavior. Product integrators use it when combining accessories such as answering machines, handsfree units, modems or PSTN adapters with a terminal. Buyers and technical reviewers use it to judge whether a terminal/accessory combination is intended for interoperable use.

Which standards are used with SIST I-ETS 300 245-4 E1:2003?

Normative reference	What it contributes
ETS 300 001	General technical requirements for equipment connected to an analogue subscriber interface in the PSTN.
I-ETS 300 004	Transmission characteristics at 2-wire analogue interfaces of a digital PABX, used in Z analogue testing and comparisons.
ETS 300 047, Parts 1-3	Safety and protection requirements for ISDN basic access.
ETS 300 085	Attachment requirements for 3.1 kHz telephony handset terminals.
ETS 300 102-1	Layer 3 basic call control specifications for the ISDN user-network interface.
ETS 300 102-2	SDL diagrams for the layer 3 basic call control specification.
I-ETS 300 245	The related parts 1, 2, 3, 5 and 6 of the ISDN telephony terminal series.
I-ETS 300 281	Requirements for end-to-end compatibility of the 7 kHz telephony teleservice.
CCITT Recommendation G.122	Assumptions on the influence of national systems on stability and echo.
CCITT Recommendation G.223	Assumptions for noise calculations on hypothetical reference circuits.
CCITT Recommendation G.711	PCM coding of voice frequencies.
ITU-T Recommendation G.712	Transmission performance characteristics of PCM channels, used for limits and test interpretation.
CCITT Recommendation G.722	7 kHz audio coding within 64 kbit/s.
CCITT Recommendation O.41	Psophometer requirements for telephone-type circuits.
FCC 68.500	The connector reference called out as the “western plug”.
ISO Publication 3	Preferred numbers, used where preferred-number series are needed.
ETS 300 082	End-to-end compatibility for the 3.1 kHz telephony teleservice.

What does the SIST I-ETS 300 245-4 E1:2003 document contain?

The document contains the application overview in clause 4, including a table of possible AEI uses and notes on how different functions may be realised. It then gives the physical and transmission rules for X- and Y-side interfaces in clause 5, including wiring, cable length, connector guidance and the separate treatment of analogue and signalling paths.

Clause 6 sets out the Z-related interface specifications, safety and protection points, and connector wiring. Clause 7 states the signalling meaning on the Z interface, and clause 8 gives the Y-interface protocol model, layer 1 framing, layer 2 message handling, layer 3 message set, call handling examples, state transition diagram and SDL description.

Annex A contains the test philosophy and the detailed test principles. It explains how to structure each test and provides test principles for XTE, YTE, XAE, YAE and Z, including the special cases for analogue and digital evaluation.

SLOVENSKI STANDARD
01-december-2003
'LJLWDOQRRPUHåMH]LQWHJULUDQLPLVWRULWYDPL,6'1±7HKQLþQHNDUDNWHULVWLNH
WHOHIRQVNLKWHUPLQDORY±GHO9PHVQLN]DGRGDWQRRSUHPR$(,
Integrated Services Digital Network (ISDN); Technical characteristics of telephony
terminals; Part 4: Additional Equipment Interface (AEI)
Ta slovenski standard je istoveten z: I-ETS 300 245-4 Edition 1
ICS:
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERIM
EUROPEAN I-ETS 300 245-4
TELECOMMUNICATION February 1995
STANDARD
Source: ETSI TC-TE Reference: T/TE 10-07(D)
ICS: 33.080
ISDN, telephony terminals, Additional Equipment Interface
Key words:
Integrated Services Digital Network (ISDN);
Technical characteristics of telephony terminals;
Part 4: Additional Equipment Interface (AEI)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - [e-mail]
X.400: Internet:
Tel.: [phone] - Fax: [phone]
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1995. All rights reserved.
New presentation - see History box

Page 2
I-ETS 300 245-4: February 1995
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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I-ETS 300 245-4: February 1995
Contents
Foreword .9
1 Scope .11
2 Normative references.11
3 Definitions and abbreviations .13
3.1 Definitions .13
3.2 Abbreviations .13
4 Applications and functionality .14
4.1 General .14
4.2 Applications.14
4.3 Functionality.16
4.3.1 Functionality of the X/Y-interface .16
4.3.2 Functionality of the Z /Z interfaces .16
A B
4.4 Operating modes .17
4.4.1 General.17
4.4.2 D-channel signalling .17
4.4.2.1 Outgoing call.17
4.4.2.2 Incoming call.17
4.4.3 Operating modes with X-/Y- interface .17
4.4.4 Operating modes with Z /Z - interface .18
A B
5 Physical and transmission requirements for X- and Y- interface .18
5.1 General .18
5.2 XTE-interface.20
5.2.1 General.20
5.2.2 Relative levels .20
5.2.3 Interface impedances.21
5.2.4 Variation of gain with the input level.21
5.2.5 Distortion .21
5.2.6 Attenuation/Frequency distortion of the encoding or the decoding side.21
5.2.7 Out-of-band signals.21
5.2.8 Single frequency noise from the encoding or decoding side.22
5.2.9 Noise .22
5.2.10 Group Delay .22
5.2.11 Short-circuit protection .22
5.2.12 Terminal Coupling Loss (TCL) .22
5.3 YTE-interface.23
5.3.1 General.23
5.3.2 Bit rate .23
5.3.3 Format.23
5.3.4 Sending .24
5.3.5 Receiving.24
5.4 XAE-interface.25
5.4.1 General.25
5.4.2 Sending .25
5.4.3 Receiving.26
5.5 YAE-interface.26
5.5.1 General.26
5.5.2 Bit rate .26
5.5.3 Format.27
5.5.4 Sending .27
5.5.5 Receiving.27
5.6 AEI-connector (X,Y).27

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I-ETS 300 245-4: February 1995
6Z /Z Interfaces Specifications . 28
A B
6.1 2-Wire Z analogue interface specification . 28
A
6.1.1 General configuration for testing Z analogue interface . 28
A
6.1.2 2-Wire Z analogue interface characteristics. 28
A
6.1.3 Voice frequency parameters of the connection between the 2-wire Z
A
interface and the digital interface of the TE and reverse . 29
6.1.4 Terminal balance return loss . 30
6.2 Z interface specification . 30
B
6.2.1 Z electrical requirements (TE output access). 30
BR
6.2.2 Z electrical requirements (TE input access) . 31
BT
6.3 Safety and protection .31
6.4 AEI connector (Z) . 31
7 Signalling protocol on the Z /Z interface . 32
A B
7.1 Significance of the signals at the Z interface . 32
B
7.1.1 At Z . 32
BR
7.1.2 At Z . 32
BT
8 Protocol of the Y-interface . 32
8.1 Model of protocol specification. 32
8.2 Layer 1 . 33
8.3 Layer 2 . 34
8.3.1 Layer 2 functions . 34
8.3.2 Structure of layer 2 messages. 34
8.3.3 Y-Message types of layer 2 . 35
8.3.4 Length indicator of layer 2. 35
8.3.5 Additional message on layer 2. 35
8.3.6 Layer 2 to layer 3 service elements . 36
8.3.7 Layer 2 timer. 36
8.3.8 Protocol principles of layer 2. 37
8.3.9 Layer 2 SDL-description . 38
8.3.10 Error handling . 41
8.4 Layer 3 . 41
8.4.1 Layer 3 functions . 41
8.4.2 Examples for layer 3 message handling. 41
8.4.2.1 Call establishment (outgoing call initiated by the AE) . 41
8.4.2.2 Call release in case of a complete established connection 42
8.4.2.3 Takeover of the current connection . 43
8.4.2.4 Incoming call . 44
8.4.2.5 Manufacturer specified applications. 45
8.4.3 Structure of layer 3 message. 46
8.4.4 Message functional definitions and contents. 46
8.4.4.1 Messages. 47
8.4.4.2 Y Setup . 48
-
8.4.4.3 Y Call answering . 49
-
8.4.4.4 Y Channel connected. 49
-
8.4.4.5 Y Channel disconnected. 49
-
8.4.4.6 Y Info. 50
-
8.4.4.7 Y Alert . 50
-
8.4.4.8 Y Call proceeding. 50
-
8.4.4.9 Y User info . 51
-
8.4.4.10 Y Transfer to TE . 51
-
8.4.4.11 Y Additional Equipment Request . 51
-
8.4.4.12 Y additional equipment acknowledge . 52
-
8.4.4.13 Y Additional Equipment Reject . 52
-
8.4.4.14 Y End . 52
-
8.4.4.15 Y Reset . 52
-
8.4.4.16 Y Terminal Active. 53
-
8.4.4.17 Y Facility. 53
-
8.4.4.18 Y Escape. 53
-
8.4.4.19 Y Disconnect. 54
-
8.4.4.20 Y Congestion Control. 54
-
8.4.5 Coding of message types . 55

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I-ETS 300 245-4: February 1995
8.4.6 Y Call Reference .55
-
8.4.7 Information elements.56
8.4.7.1 Coding of information elements.56
8.4.7.2 Priority.56
8.4.7.3 Manufacturer identifier.57
8.4.8 Layer 3 timer .57
8.4.9 State transition diagram .57
8.4.10 Layer 3 SDL-Description .65
8.4.11 Error handling.78
Annex A (normative): Test specification.79
A.1 Definitions of the aim of the test specification.79
A.2 Definition of the structure of the test principles .79
A.3 Definition of terms .80
A.4 Definition of special test equipment .81
A.4.1 AE and TE - simulator.81
A.4.2 Test instruments .81
A.5 General condition for testing .82
A.5.1 General .82
A.5.2 Conditions for testing Z analogue interface.83
A
A.6 Test principles .84
A.6.1 Test principles XTE (X-interface at TE).84
A.6.1.1 Relative levels .84
A.6.1.1.1 Input (TP No. 1) .84
A.6.1.1.2 Output (TP No. 2) .84
A.6.1.2 Interface impedances.85
A.6.1.2.1 Input (TP No. 3) .85
A.6.1.2.2 Output (TP No. 4) .86
A.6.1.3 Variation of gain with input level.86
A.6.1.3.1 Encoding side (TP No. 5) .86
A.6.1.3.2 Decoding side (TP No. 6) .87
A.6.1.4 Distortion .88
A.6.1.4.1 Encoding side .88
A.6.1.4.1.1 Distortion as a function of input level
(TP No. 7) .88
A.6.1.4.1.2 Distortion as a function of frequency
(7 kHz telephony) (TP No. 8) .88
A.6.1.4.2 Decoding side.89
A.6.1.4.2.1 Distortion as a function of input level
(TP No. 9) .89
A.6.1.4.2.2 Distortion as a function of frequency
(7 kHz telephony) (TP No. 10) .90
A.6.1.5 Attenuation/Frequency distortion of the encoding or decoding side.90
A.6.1.5.1 Encoding side (TP No. 11) .90
A.6.1.5.2 Decoding side (TP No. 12) .91
A.6.1.6 Out-of-band signals.92
A.6.1.6.1 Discrimination against out-of-band input signals (TP No.
13).92
A.6.1.6.2 Spurious out-of-band signals at the output (TP No. 14) .92
A.6.1.7 Single frequency noise .93
A.6.1.7.1 Encoding side (TP No. 15) .93
A.6.1.7.2 Decoding side (TP No. 16) .94
A.6.1.8 Noise .95
A.6.1.8.1 Input (TP No. 17) .95
A.6.1.8.2 Output (TP No. 18) .95
A.6.1.9 Group delay.96
A.6.1.9.1 Encoding side (TP No. 19) .96

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I-ETS 300 245-4: February 1995
A.6.1.9.2 Decoding side (TP No. 20). 97
A.6.1.10 Short circuit protection (TP No. 21) . 99
A.6.1.11 Terminal Coupling Loss (TCL) (TP No. 22). 99
A.6.2 Test principles YTE (Y-interface at TE). 100
A.6.2.1 Bit rate . 100
A.6.2.1.1 Transmitting bit rate (TP No. 23). 100
A.6.2.1.2 Receiving bit rate (TP No. 24). 100
A.6.2.2 Format (TP No. 25). 101
A.6.2.3 Sending. 102
A.6.2.3.1 Active state, with load (TP No. 26). 102
A.6.2.3.2 Active state, without load (TP No. 27). 102
A.6.2.3.3 Idle state (TP No. 28). 103
A.6.2.3.4 Output resistance (TP No. 29) . 103
A.6.2.4 Receiving . 104
A.6.2.4.1 Short-circuit current (TP No. 30). 104
A.6.2.4.2 Open-circuit voltage (TP No. 31) . 105
A.6.3 Test principles XAE (X-interface at AE) . 106
A.6.3.1 Sending. 106
A.6.3.1.1 Output level (TP No. 32) . 106
A.6.3.1.2 Active mode output impedance (TP No. 33). 106
A.6.3.1.3 Idle mode insertion loss (TP No. 34). 107
A.6.3.1.4 Noise (TP No. 35) . 107
A.6.3.2 Receiving . 108
A.6.3.2.1 Input impedance (TP No. 36). 108
A.6.4 Test principles YAE (Y-interface at AE) . 108
A.6.4.1 Bit rate . 108
A.6.4.1.1 Transmitting bit rate (TP No. 37). 108
A.6.4.1.2 Receiving bit rate (TP No. 38). 109
A.6.4.2 Format (TP No. 39). 109
A.6.4.3 Sending. 110
A.6.4.3.1 Active state (TP No. 40). 110
A.6.4.3.2 Idle state (TP No. 41). 111
A.6.4.4 Receiving . 111
A.6.4.4.1 Active state (TP No. 42). 111
A.6.4.4.2 Idle state (TP No. 43). 112
A.6.5 Test principles Z . 112
A
A.6.5.1 2-wire Z analogue interface requirements testing . 112
A
A.6.5.1.1 Return loss (TP No. 44) . 112
A.6.5.1.2 Superimposed DC voltage (TP No. 45) . 113
A.6.5.1.3 Maximum loop current (TP No. 46). 114
A.6.5.1.4 Loop threshold current (TP No. 47) . 114
A.6.5.2 Voice frequency parameters of the connection between the 2-wire Z
A
interface and the digital interface of the TE and reverse . 115
A.6.5.2.1 Transmission loss (sending direction) (TP No. 48). 115
A.6.5.2.2 Transmission loss (receiving direction) (TP No. 49). 116
A.6.5.2.3 Variation of gain with input level (sending direction) (TP
No. 50) . 117
A.6.5.2.4 Variation of gain with input level (receiving direction) (TP
No. 51) . 118
A.6.5.2.5 Loss distortion with frequency (sending direction) (TP No.
52). 119
A.6.5.2.6 Loss distortion with frequency (receiving direction) (TP
No. 53) . 120
A.6.5.2.7 Discrimination against out of band signals applied to the
Z analogue interface (TP No. 54) . 121
A
A.6.5.2.8 Spurious out of band received at the Z analogue
A
interface (TP No. 55). 122
A.6.5.2.9 Total distortion, including quantizing distortion (sending
direction) (TP No. 56). 123
A.6.5.2.10 Total distortion including quantizing distortion (receiving
direction) (TP No. 57). 124
A.6.5.2.11 Weighted noise at S digital interface (TP No. 58). 125
A.6.5.2.12 Weighted noise at Z analogue interface (TP No. 59) . 126
A
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I-ETS 300 245-4: February 1995
A.6.5.3 S/T digital interface testing .127
A.6.5.3.1 Terminal balance return loss (TP No. 60) .127
A.6.6 Test principles Z (B-interface at TE).128
B
A.6.6.1 Z electrical requirements (TE output access).128
BR
A.6.6.1.1 Active state without load (TP No. 61) .128
A.6.6.1.2 Active state with load (TP No. 62) .128
A.6.6.1.3 Idle state with load (TP No. 63) .129
A.6.6.2 Z electrical requirements/TE input access.129
BT
A.6.6.2.1 Active state control voltage (TP No. 64) .129
A.6.6.2.2 Active state input current (TP No. 65) .130
A.6.6.2.3 Idle state control voltage (TP No. 66) .130
A.6.6.2.4 Idle state driving current (TP No. 67).130
Annex B (informative): Bibliography.131
History.132

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I-ETS 300 245-4: February 1995
Foreword
Part 4 of this Interim European Telecommunication Standard (I-ETS) was produced by the Terminal
Equipment (TE) Technical Committee of the European Telecommunications Standards Institute (ETSI).
An ETSI standard may be given I-ETS status either because it is regarded as a provisional solution ahead
of a more advanced standard, or because it is immature and requires a "trial period". The life of an I-ETS
is limited to three years after which it can be converted into a European Telecommunication Standard
(ETS), have it's life extended for a further two years, be replaced by a new version or, be withdrawn.
This is the fourth Part of an I-ETS which is currently intended to comprise eight Parts.
This I-ETS specifies technical characteristics for Integrated Services Digital Network (ISDN) telephony
terminals as described in the scope of this I-ETS. The characteristics are additional to type approval
requirements to which the terminal equipment is subject. The additional characteristics are meant to give
improved performance.
In the present version of the I-ETS the following Parts are included:
Part 1: General (I-ETS 300 245-1);
Part 2: PCM A-Law, Handset Terminals;
Part 3: PCM A-Law, Loudspeaking and Handsfree Telephony;
Part 4: Additional Equipment Interface;
Part 5: Wideband Coding Handset Functions;
Part 6: Wideband Coding Loudspeaking and Handsfree Telephony;
Part 7: Locally Generated Information Tones;
Part 8: Terminal Application of 16 kbit/s Speech Coding Algorithms.
Proposed announcement date
Date of latest announcement of this I-ETS (doa): 31 May 1995

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I-ETS 300 245-4: February 1995
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I-ETS 300 245-4: February 1995
1 Scope
This Interim European Telecommunication Standard (I-ETS) specifies the technical characteristics
(physical, electrical, logical and functional) of a family of interfaces for the connection of additional
equipment to ISDN telephony terminals. These interfaces support the facilities and services applicable
mainly to ISDN telephony teleservices associated with those functions.
Two interfaces allow bi-directional transparent analogue transmission of B-channel information between
the telephony terminal and the additional equipment with a bandwidth of 3,1 kHz or 7 kHz. Both a "2-wire"
(Z -I)and a "4-wire" interface (X-I) are described.
A
Two other interfaces allow the transmission of D-channel related information between the telephony
terminal and the additional equipment. One (Y-I) uses a "4-wire" bi-directional data line with an
asynchronous digital transmission. This interface can be implemented separately or in combination with
any of the two interfaces for B-channel information. The second one (ZB-I) transmits ON/OFF signalling
data in both directions. This interface can be implemented separately or in combination with the "2-wire"
interface.
The digital telephony terminal may support one or a combination of the following interfaces as an option:
- "4-wire" analogue interface (3 wires, including common ground);
- "4-wire" digital signalling interface (3 wires, including common ground);
- "2-wire" analogue interface;
- ON/OFF signalling interface (3 wires, including common ground).
Annex A to this I-ETS specifies the methods of testing required to identify conformance to this I-ETS.
This fourth Part of I-ETS 300 245 is applicable as one option to telephony terminals as specified in other
Parts of this I-ETS, and additional equipment intended to be connected to these terminals.
NOTE: The specification of the "2-wire" interface is presently based on the requirements which
can be satisfied by many analogue terminals connected through a very short line
directly or via an adapter (Videotext terminals, PC modem, etc.). Appropriate
alternatives could be the requirements resulting from the on-going harmonisation
activities aiming enhancement of I-ETS 300 004 [2] or ETS 300 001 [1] (related
respectively to the Private Branch eXchange (PBX) or Public Network analogue
interface).
2 Normative references
This fourth Part of the I-ETS incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of
these publications apply to this fourth Part of the I-ETS only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies.
[1] ETS 300 001: "Attachments to Public Switched Telephone Network (PSTN);
General technical requirements for equipment connected to an analogue
subscriber interface in the PSTN (Candidate NET 4)".
[2] I-ETS 300 004 (1991): "Business Telecommunications (BT); Transmission
characteristics at 2-wire analogue interfaces of a digital Private Automatic
Branch Exchange (PABX)".
[3] ETS 300 047, Parts 1-3 (1992): "Integrated Services Digital Network (ISDN);
Basic access; Safety and Protection".
[4] ETS 300 085 (1990): "Integrated Services Digital Network (ISDN) - 3,1 kHz
telephony teleservice - Attachment requirements for handset terminals".
[5] ETS 300 102-1 (1990): "Integrated Services Digital Network (ISDN) - User-
network interface layer 3 - Specifications for basic call control".

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I-ETS 300 245-4: February 1995
[6] ETS 300 102-2 (1990): "Integrated Services Digital Network (ISDN) -
User-network interface layer 3 - Specifications for basic call control -
Specification Description Language (SDL) diagrams".
[7] I-ETS 300 245: "Integrated Services Digital Network (ISDN) - Technical
characteristics of telephony terminals - Parts 1, 2, 3, 5, 6".
[8] I-ETS 300 281 (1994): "Integrated Services Digital Network (ISDN) - Telephony
7 kHz teleservice - Terminal requirements necessary for end-to-end
compatibility".
[9] CCITT Recommendation G.122 (1988): "Influence of national systems on
stability - talker echo and listener echo in international connections".
[10] CCITT Recommendation G.223 (1988): "Assumptions for the calculation of
noise on hypothetical reference circuits for telephony".
[11] CCITT Recommendation G.711 (1988): "Pulse code modulation (PCM) of voice
frequencies".
[12] ITU-T Recommendation G.712 (1992): "Transmission performance
characteristics of pulse code modulation channels".
[13] CCITT Recommendation G.722 (1988): "7 kHz audio-coding within 64 kbit/s".
[14] CCITT Recommendation 0.41 (1988): "Psophometer for use on telephone-type
circuits".
[15] FCC 68.500 (1988): "Code of federal regulations/telecommunication 47 - parts
40 to 69".
[16] ISO Publication 3 (1973): "Preferred numbers - series of preferred numbers".
[17] ETS 300 082 (1992): "Integrated Services Digital Network (ISDN) - 3,1 kHz
telephony teleservice - End-to-end compatibility".

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I-ETS 300 245-4: February 1995
3 Definitions and abbreviations
3.1 Definitions
For the purposes of this Part of the I-ETS, the relevant definitions used in the referenced CCITT
Recommendations and ETSs, and the following definitions apply:
Additional Equipment (AE): Equipment to be connected at the ISDN telephony terminal to support
additional functions.
Additional Equipment Interface (AEI): Interface to connect an additional equipment.
dBr: Relative level to the 0 dBr point basic user-network interface according to CCITT Recommendation
G.101.
X-Interface (X-I): Analogue interface which provides bi-directional transmission of B-channel related
information between a telephony terminal and an additional equipment.
XTE-Interface: X-interface on the Terminal Equipment side.
XAE-Interface: X-interface on the Additional Equipment side.
Y-Interface (Y-I): Digital interface which provides bi-directional transmission of signalling messages
between a telephony terminal and an additional equipment.
YTE-Interface: Y-interface on the Terminal Equipment side.
YAE-Interface: Y-interface on the Additional Equipment side.
Z -Interface (Z -I): Analogue interface which provides bi-directional transmission over the access
A A
channel.
Z -Interface (Z -I): Interface to transmit signalling information.
B B
3.2 Abbreviations
For the purposes of this Part of the I-ETS, the abbreviations used in the referenced CCITT
Recommendations, ETSs and the following abbreviations apply:
AE Additional Equipment
AEI Additional Equipment Interface
ET Exchange Termination
ETS European Telecommunication Standard
I-ETS Interim European Telecommunication Standard
ISDN Integrated Services Digital Network
PBX Private Branch eXchange
S/T ISDN-Basic User Network Interface
TE Terminal Equipment
X-I X-Interface
Y-I Y-Interface
Z -I Z -Interface
A A
Z -I Z -Interface
B B
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I-ETS 300 245-4: February 1995
4 Applications and functionality
4.1 General
The AEI supports and extends the functionality of an ISDN telephony terminal. Various sets of equipment
and applications can be realised using the interfaces as specified in clauses 5 and 6 (Physical and
Transmission requirements) and in clauses 7 and 8 (Protocols of layers 2 and 3).
The additional functionality's require appropriate extensions of the terminal software in order to take into
account the interface towards the AE and/or the application itself.
According to the type of additional equipment, which is connected to the ISDN terminal, it should be noted
that not only the functionality is influenced due to supporting or extending by the additional equipment, but
also the transmission performance for speech is influenced additionally according to the special
transmission parameters of the additional equipment and the transmission characteristics of the interface
as far as the access channel is concerned. But the specification of these parameters is out of the scope of
this I-ETS. The overall performance of the terminal configuration may be determined mainly by the
additional equipment. For these cases the ISDN terminal could be considered functionally as a carrier.
That could be important for aspects for network planning whereby the effective Terminal Coupling Loss
(TCL) respectively the echo return loss should be considered particularly.
4.2 Applications
This equipment and applications use parts or the whole functionality of the various interface types.
A possible set is described in table 1.

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I-ETS 300 245-4: February 1995
Table 1: Possible applications
XY Z Z Application
A B
XX Second earphone
note 1
X Loudspeaking equipment
note 2 Handsfree equipment
note 3 note 3 Additional alerting module
X Call monitor
AE which interprets the call related D-channel messages and supports
additional information to them.
X X X X Automatic answering machine
It answers an incoming call and allows the store of an incoming
message.
X X X X Speech recording
X note 4 Dialling function
To set-up an outgoing call by an AE.
X X X X Alarm equipment
X X Charging device
An AE which prints or stores the charging information (e.g. called party
number and charging units).
X X Speech cryptography
note 5 note 5 note 5 X Modem / Videotexterminal
Support of data transmission (e.g. file transfer) or Videotex.
X X X X PSTN - adapter
Adapter to connect conventional analogue PSTN-terminals. The
note 6 note 6 note 6 note 6
analogue line-interface shall be compatible with ETS 300 001 [1].
FFS FFS FFS FFS Tele-Writing
FFS FFS FFS FFS Tele-Drafting
FFS FFS FFS FFS Control of videophone terminal
FFS FFS FFS FFS Test utility
FFS FFS FFS FFS Down loading
NOTE 1: This application is listed only with respect to completeness of possibilities, but is not
recommended.
NOTE 2: TE need a procedure to activate the X-input channel without the use of the Y-signalling
information.
NOTE 3: Additional alerting module can be realised either by the Y-interface or the Z -interface.
B
NOTE 4: DTMF signalling may be transmitted through the Z -interface.
A
NOTE 5: Application can be realised either by the X and Y-interface or the Z -interface.
A
NOTE 6: Not intended for connection of normal telephones.

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I-ETS 300 245-4: February 1995
4.3 Functionality
4.3.1 Functionality of the X/Y-interface
To realise the various applications and equipment the different interface types need special functions.
These functions have been defined on the basis of existing and future additional equipment.
The main functions are listed in the following:
- call establishment
A call can be established by an AE via the telephony terminal.
- call release
A connection can be released by an AE (e.g. automatic answering machine).
- sending dialling information
Dialling information can be sent by an AE in case of call establishment (e.g. dialling
equipment, alarm equipment, etc.).
- receiving dialling information
− receiving calling line identity
An AE can know the calling party number receiving in an incoming call.
− receiving called party number
An AE can receive information or acknowledgement of the called party number
transmitted by the TE when a new call is established.
- priority control
- priority for the AE
In the case of alarm equipment, the AE shall have the possibility to disconnect an
established connection of the telephony terminal, to send its alarm message.
- priority for the telephony terminal
If an automatic answering machine is connected to the telephony terminal and a
connection is held by the AE, the telephony terminal can take over the connection from
the AE.
- call transfer between TE and AE
An established call can be transferred between the telephony terminal and an AE by a
manual procedure or in case of priority control by an automatic procedure.
- receiving charging information
- handling of user-to-user information
For further study.
- exit for manufacturer specific signalling information
See subclause 8.4.2.5.(message type ESCAPE).
-transmission of transparent access channel information
Send and receive direction.
- cascading of AE
Restriction with respect to cascading of AE (see subclauses 5.1 and 8.1).
4.3.2 Functionality of the Z /Z interfaces
A B
According to the application, this interface allows the functions listed below:
- call set-up
- by the user dialling on the TE;
- automatically to an address previously registered in the TE.
- call answer
- from the TE by the user;
- automatically from the AE by activation of incoming call forwarding or using a different
address (or another bearer capability).
- connection switching
- from TE to AE and possibly reduced to one direction (e.g. additional earphone).
- call release
- from the TE;
- from the AE.
- transmission of control signals
- for instance: additional alerting module, charging pulse counter, automatic answering
machine.
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I-ETS 300 245-4: February 1995
4.4 Operating modes
4.4.1 General
The TE may have different operating modes according to the following options:
a) availability of one or two codecs;
b) use of one or two addresses;
c) use of one or several bearer services.
When the terminal has two codecs it can handle two calls simultaneously, however, care shall be taken to
avoid blocking; this means that one B-channel (any one) shall be used for the TE while the other is
connected to the AE.
When the terminal has been given different addresses (or subaddresses, or bearer services), one could
be associated to the TE while the other one is attached to the AE
...