Integrated Services Digital Networks - ISDN
The Public Switched Telephone Network
- telephones in POTS become more complex supporting voice, video and data
Digital TDM Switching
- digital TDM replaces analog FDM
Subscriber Loop (digitized voice, etc)
- full duplex digital transmission from the user to end office switch (TDM with PCM)
Control Signaling
- common channel signaling over a packet switched network embedded in the PSTN for control, routing, monitoring, AIN services