ISDN interface unit with separate ring generator

An ISDN interface apparatus for processing an interface process to an ISDN and to an analog telephone, comprising:

• an ISDN interface unit having a ring signal controller for supplying a control signal to designate a generation of a ring of the analog telephone when a connection is designated to the analog telephone from the ISDN;
• and
• a ring signal generator unit, connected to the ISDN interface unit through a first modular jack and connected to the analog telephone through a second modular jack, having a ring signal generator for generating a ring signal to obtain the ring of the analog telephone and switch means for selecting one of the ring signal generated by the ring signal generator and a voice signal output through the first and second modular jacks and for supplying the selected signal to the analog telephone, wherein
• the switch means supplies the ring signal generated by the ring signal generator to the analog telephone when the ring signal controller outputs the control signal.