3.10 Interoperability

Introduction

Section 376 of the Telecommunications Act 1997 empowers the ACMA to make Technical Standards for Customer Equipment (CE) and Customer Cabling (CC) in relation to a restricted list of matters. In particular, it provides for Standards that contain requirements necessary or convenient for:

• ensuring that CE can be used to give access to an emergency call service; or
• ensuring, for the supply of the Standard Telephone Service (STS), the interoperability of CE with a telecommunications network to which the CE is, or is proposed to be, connected.

Section 18 of the Telecommunications Act 1997 provides some guidance on access to emergency call service, in which a person should be able to establish and maintain a call to the emergency service number.

The ACMA is expected to also to consider matters that arise from the Council of Australian Governments (COAG) Guidelines on regulatory Standards and the need to prepare regulatory impact statements which may lead it to decide to exercise its powers to a lesser extent. As a result, Working Committees should not consider technical requirements in isolation and must consider the costs and benefits arising from the requirements they propose.

The following guidelines are intended to assist Communications Alliance Working Committees in determining what matters should be addressed in new or revised Standards the Communications Alliance is to propose to the ACMA.

This guidance should be read in conjunction with the guidance on assessing Network Integrity Items. Note that the guidance on network integrity and on interoperability is neither exhaustive nor exclusive and Working Committees are advised to use them as a reference guide in testing each clause for interoperability or access to emergency service numbers.

Because the actual clauses in the Standards are so varied and have a range of impacts, the use of examples of the matters that could be relevant is the best approach. The examples provided may be relevant for a particular Standard and should be evaluated in the context of the Standard to assess whether related requirements are required to ensure the interoperability of CE for the STS with a telecommunications network or facility operated by a C/CSP or to ensure access to an emergency call service.

A key point to consider is that a simplistic interpretation and application of the expression interoperability with the telecommunications network or facility could be that it only refers to the CE operating with the C/CSP’s network alone. That is, it does not recognise CE at the far end and the need to establish a connection between the two. From the practical viewpoint, it requires end users supplied with the same service being ordinarily able to communicate between each other whether or not the end users are connected to the same network.

Interoperability, for the purpose of the supply of a STS, can be considered to relate to the three phases of:

• Call set-up;
• Information transfer; and
• Call clear-down.

The first and third are aligned with the signalling functions of the CE while the information transfer is primarily dependent on the transmission performance of the CE.

This Guideline also discusses issues concerning equivalent forms of communication for an end user with a disability. The Disability Matters: Access to Communication Technologies for People with Disabilities and Older Australians Industry Guideline (G586:2006) provides assistance for Communications Alliance Reference Panels and Working Committees to meet their responsibilities under the Disability Discrimination Act 1992 and the Telecommunications (Consumer Protection and Service Standards) Act 1999 and to assist Communications Alliance and its Reference Panels and Working Committees to provide equity in access to telecommunications for people with disabilities.

Signalling

a) Line Polarity

Where CE is required to recognise the polarity of the line to identify the condition of the line prior to initiating a call then the response to these conditions may need to be specified e.g. reversal on idle.

b) Looping the line (breaking dial tone)

CE resistance characteristics as a function of time determine the ability of the CE to loop the line. Therefore the network line port voltage-current characteristics may need to be specified for looping the line and throughout the duration of the connection.

c) Dialling

To establish a connection using the STS to a C/CSP’s telecommunications network or facility will require a destination number to be dialled after the line is looped. The characteristics of the dialling process affect the reliability and accuracy of the telecommunications network or facility in recognising the dialled digits and hence setting up the connection. Therefore the decadic, DTMF and MFC signalling characteristics would need to be specified. Similarly to ensure end-to-end interoperability it would seem that the correct reception of dialled digits on an indial circuit would also need to be considered. Possible misoperation by the end-user may also need to be considered, for example poor identification, layout or design of end-user accessible parts or end-user programmable software.

d) Incoming Call Recognition

To establish a connection using the STS to a C/CSP’s telecommunications network or facility, requires the destination CE to be able to recognise that an incoming call is being offered and is available to be answered. For indial circuits, the correct reception of dialled digits may need to be considered. Therefore the CE must be able to:

• recognise the incoming call state (e.g. ringing on a ring-in loop-out service).
• indicate to the called party that a call is being offered for answering.
• apply the correct answering conditions to the line.

e) Clear Down

Although clear down directly relates to network integrity there is also a close link to interoperability as the CE should be able to clear down a connection and establish another connection as required. Therefore, requirements defining the clear down process signalling and the actual loop disconnect process (if used) would need to be considered.

Transmission

a) Send and Receive Loudness ratings

For the user to recognise network tones e.g. dial tone, the receive loudness rating would need to be adequate. To distinguish a specific tone within a range of network tones both the receive loudness rating and the distortion performance would need to be satisfactory. To enable the reliable transfer of information to the other party in a connection, e.g. an emergency service operator, the send loudness rating and the distortion performance of the sending CE must be specified to be within certain limits. To understand the emergency service operator, the receive performance must be satisfactory.

This then suggests that both the send and receive loudness ratings plus at least the send distortion performance should be considered.

b) Distortion

As noted above, distortion limits should apply to the send performance. Distortion limits could also apply to the receive performance however this is more difficult compared with the send performance and is probably not warranted in practice.

c) Noise

The overall information transfer on a connection will be dependent, inter alia, on the loudness loss between the two items of CE and the noise level on the circuit. Therefore consistent with specifying the loudness ratings and distortion, the noise performance on both send and receive would need to be considered.