3.11 Definition of the Standard Telephone Service


The following guidance is to assist Working Committees in making decisions as to the application of the Standard Telephone Service (STS) definition to Customer Equipment (CE) Standards. It should be noted that there is an inherent difficulty in doing this:

  • the STS is defined in Section 6 of the Telecommunications (Consumer Protection and Service Standards) Act 1999 and is paraphrased in Clause 6.2; but
  • there is no corresponding definition of a Standard Telephone Instrument.

Many types of CE and interfaces may in fact deliver a voice carriage service. Therefore while this Guideline can point to key considerations it cannot stand in place of the need for the Working Committee to make some assessment or seek external guidance from the CECRP as to whether a given CE is a means of connecting to an STS.

Application of the STS definition to requirements in CE Standards

The STS may be defined as a carriage service for the purpose of voice telephony communication (or an equivalent form of communication for an end user with a disability) between end-users supplied with the same service, whether or not the end users are connected to the same telecommunications network.

NOTE 1: The common equivalent forms of communication are to use data to provide text communication via CE, e.g. TTY, Text Telephone, Modem, TeleBraille. These devices may interface to a carrier’s network using, for example, Baudot, V.21, V.18, EDT, V.23 and CTM. These CE are used by people who may be deaf, hearing impaired, speech impaired, deaf/blind and deaf/visually impaired and may have single or multiple disabilities.

NOTE 2: It is the purpose of the technology, not the technology itself, that is the key point of the application of the STS in providing equivalent service. For example, TTY is used to provide an equivalent service to the STS.

The above definition paraphrases the standard telephone service definition in Section 6 of the Telecommunications (Consumer Protection and Service Standards) Act 1999. Important points to note:

  • the definition covers carriage services which terminate at a Carrier’s network boundary and which are available for interfacing to CE. It does not cover CE interfaced to that service.
  • ‘voice telephony between end users’ implies call set-up and real-time two-way communication.
  • the definition of STS is independent of the technology used by the carrier for the transmission and delivery of the voice signal.
  • the definition of STS in the Telecommunications (Consumer Protection and Service Standards) Act 1999 also covers other forms of communication equivalent to voice telephony for end users with a disability, e.g. to allow people to communicate via methods other than speaking and/or hearing.

Some examples of technologies which may be used to deliver an STS include:

  • analogue transmission within the voice frequency band, e.g. on a twisted pair copper line, 4-wire leased line.
  • digital transmission, e.g. basic access and primary rate ISDN or PCM channels on an E1 link.
  • transmission to/from remote network interface units over various media, e.g. remote switches, remote multiplexers, analogue or digital pair gain, HFC, FTTP, WLL, satellite.

The network interface units will present digital or analogue interfaces as referred to above, at the network boundary.

In Note 2 of Schedule 1 of the Telecommunications Labelling (Customer Equipment and Cabling) Notice 2001 there is an exception to network interoperability for packet based technologies, e.g. ATM. for earlier revisions of some Standards.

Indicating mandatory requirements for CE interfaced with a STS

In each Communications Alliance Standard, in the Interpretative Guidelines Section under the Categories of Requirements clause, the following wording shall be incorporated stating the applicability of requirements to STS:

‘Clauses qualified as applying to ‘STS CE’ or to ‘CE used for the supply of the Standard Telephone Service’, identify requirements that are mandatory only for CE interfaced to an STS as defined by the Telecommunications (Consumer Protection and Service Standards) Act 1999.’

Equivalent CE used to provide an equivalent service to voice telephony to the STS shall be required to meet the above qualification regardless of the technology used.