Physical Layer
The ISDN Physical Layer is the first layer in the OSI model for Integrated Services Digital Network (ISDN) networking. It is responsible for the transmission and reception of raw bit streams over a physical medium.
Key characteristics include:
Interface Types: Supports two main interfaces - Basic Rate Interface (BRI) and Primary Rate Interface (PRI).
BRI: Consists of two 64 Kbps B-channels and one 16 Kbps D-channel.
PRI: Includes 23 B-channels and one 64 Kbps D-channel in North America or 30 B-channels and one D-channel in Europe.
Transmission Medium: Typically uses twisted-pair cables, but may also use fiber optics.
Functions: Converts digital signals to electrical signals and vice versa, ensuring proper timing and synchronization.
It serves as the foundation upon which higher ISDN layers build, facilitating data exchange over ISDN connections.
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