Maintenance Architecture
555-233-123
1-12 Issue 4 May 2002
■ 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 equipment and the DCE
equipment. Depending on the type of equipment used, the code can be
any proprietary code set.
■ Digital multiplexed interface proprietary — Family of protocols between the
originating DCE and the destination DCE for digital transmission. See
DEFINITY Communications System and System 75 and System 85
DS1/DMI/ISDN PRI Reference, 555-025-101; and Digital Multiplexed
Interface [DMI] Technical Specification, 555-025-204
■ Voice-grade data — Between the originating DCE and the destination DCE
for analog transmission
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