ISDN EQUIPMENT IS GOVERNED BY STANDARDS BASED ON THE OSI SEVEN-LAYER MODEL WHICH INSURE INTEROPERABILITY ...
THE ISDN PHYSICAL LAYER DEFINES HOW USER EQUIPMENT INTERFACES TO THE NETWORK ...
NOW .. PLEASE REFER MODEL DRAWING AS BELOW ... YOU SHOULD GET MUCH UNDERSTANDING WHAT'S ISDN AND HOW TO BUILD UP IT !!
REMARK :