The purpose of the Leaflet is to define, fo all lines not equipped with GSM-R: the use of fixed and portable lineside telephones as provided for train staff, maintenance gangs, station staff, and in some cases for customers; the functionality of the circuits to which the telephones are connected; the technical characteristics, for both telephones and circuits, of: the calling equipment, the supply components, the means of connection of the telephones, the method of installation.