scope:

This first part of ETS 300 659 specifies the subscriber line protocol for the support of PSTN display services at Local Exchange (LE) in "on hook" state. The subscriber line protocol is accomplished by using asynchronous voice-band Frequency-Shift Keying (FSK) signalling. In addition, annex C is provided in order to allow the continuation of use in those networks that already implemented a Dual Tone Multi-Frequency (DTMF) based subscriber line protocol.

The requirements imposed on the FSK signalling-based subscriber line protocol deal with data encoding, data transmission requirements and the three layers of the protocol at the network side of the interface: presentation layer, data link layer and physical layer.

The requirements imposed on the DTMF-based subscriber line protocol deal with the transfer of the DTMF coded display information. The procedures and the encoding arrangements are specified in annex C of this ETS.

Terminal Equipment (TE) can be connected by analogue access directly to the LE or through an Access Network (AN). In the latter case, data transmission can be applied from the LE or from elsewhere in the network hence a transmission path needs to exist from the LE to the TE before data transmission. It is the network operator's responsibility to ensure transmission path establishment. Transmission path establishment procedures are outside the scope of this ETS.