Avaya S8700 Maintenance Manual page 37

Protocols
Analog — A modulated voice-frequency carrier signal
ADU Proprietary — A signal generated by an ADU. The signal is for
communication over limited distances and can be understood only by a
destination ADU or destination system port with a built-in ADU
Digital Signal Level 1 (DS1) — A protocol defining the line coding,
signaling, and framing used on a 24-channel line. Many types of trunk
protocols (for example, PRI and 24th-channel signaling) use DS1 protocol
at layer 1.
European Conference of Postal and Telecommunications rate 1 (CEPT1)
— A protocol defining the line coding, signaling, and framing used on a
32-channel line. Countries outside the United States use CEPT1 protocol.
Inside the system, data transmission appears in one of two forms:
1. Raw digital data, where the physical layer protocols, like DCP, are stripped
at the incoming port and reinserted at the outgoing port.
2. Pulse Code Modulation (PCM)-encoded analog signals (analog
transmission by a modem), the signal having been digitized by an
analog-to-digital coder/decoder (CODEC) at the incoming port.
Layer-2 Protocols
Layer-2 protocols are given below:
8-bit character code — Between the DTE and DCE equipment.
Depending on the type of equipment used, the code can be any proprietary
code set.
Digital multiplexed interface proprietary — Between the originating and the
destination DCE. Family of protocols for digital transmission.
Voice-grade data — Between the originating and the destination DCE. For
analog transmission.
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