scope:

This European Telecommunication Standard (ETS) specifies the transmission requirements for digital Private Branch eXchanges (PBXs) (through-connecting telecommunications equipment) that: - are not part of the public network; - carry 3,1 kHz telephony between analoque interfaces, digital interfaces carrying 64 kbit/s A-law encoded signals and the acoustic interfaces of handset telephony terminals that are designed to be used together with the PBX for connections involving digital access to the public switched network.