DEREP Ethernet Repeater

This document is the Technical Manual for the DEREP Ethernet Repeater, published by Digital Equipment Corporation.

The manual provides comprehensive information on the installation, operation, and maintenance of the DEREP Ethernet Repeater, a device designed to extend Ethernet networks beyond the 500-meter (1640 ft) limit of a single coaxial cable segment.

Key aspects covered include:

1. Functional Description:

   • Local Repeater: Links Ethernet segments up to 100 meters (328 ft) apart using two 50m (164 ft) transceiver drop cables.
   • Remote Repeater: Links segments up to 1100 meters (3609 ft) apart using a fiber-optic link, providing electrical isolation and resistance to interference.
   • Operation is fully automatic and transparent to Ethernet users.

2. Physical Description: Details the components, interfaces (transceiver and fiber-optic), control switches (power, self-test, standby mode), and LED indicators for diagnostics.

3. Installation: Provides step-by-step procedures for both local and remote repeaters, including pre-installation considerations, cable connections, and initial self-testing.

4. Theory of Operation: Explains the repeater's internal states and how it manages network conditions:

   • Carrier Detection: Automatically generates and transmits preambles upon detecting carrier signals.
   • Collision Handling: Enforces collisions across segments by transmitting "jam" bits, ensuring all nodes detect the collision.
   • Segmentation (Autosegmentation): Automatically isolates a faulty segment (e.g., after 64 consecutive collisions) to prevent network disruption.
   • Standby Mode: Allows a secondary (local only) repeater to monitor a primary unit and automatically switch to active mode if the primary fails, enhancing network reliability.
   • Self-Test: Describes internal (logic module) and external (including interfaces and cables) self-test procedures initiated on power-up or via a button.

5. Technical Description: Delves into the data structure (packet, preamble) and the various internal circuits (e.g., transceiver interfaces, fiber-optic interface, collision counters, data decoder, FIFO, state machine, power supply).

6. Maintenance: Covers preventive maintenance (periodic self-testing) and corrective maintenance, including fault isolation using LED indicators, troubleshooting tips, and procedures for replacing Field Replaceable Units (FRUs) like the logic module, power supply, and fiber-optic interface.

7. Fiber-Optic Link Certification (Appendix A): Outlines essential procedures for certifying fiber-optic cable installations for remote repeaters, including visual inspection, loss calculation, FOTDR (Fiber-Optic Time Domain Reflectometer) measurements, and troubleshooting common issues like excessive attenuation.

In essence, the manual serves as a comprehensive guide for anyone responsible for deploying, understanding, or maintaining the DEREP Ethernet Repeater in a network environment.