Specifications

Test and Diagnostic Functions 4-1
Chapter 4
Tests & Diagnostics
4.1 General
This chapter provides and explains the module-specific tests and diagnostic
functions, and information on the alarms generated by the HS-R module.
The chapter also includes troubleshooting instructions.
The diagnostic information presented here supplements the general diagnostics
instructions contained in the Megaplex-2100 System Installation and Operation
Manual.
4.2 Test and Diagnostic Functions
The available test and diagnostics functions are:
• Local digital loopback on the desired module channel.
• Remote digital loopback on the desired module channel.
The following sections describe the available test activities.
Local Digital Loopback (Local Loop)
The local digital loopback is performed at the input of the digital circuits serving
the corresponding channel.
When the loopback is activated, the channel transmit signal is connected to the
input of the receive path, and is returned to the user's terminal equipment. The
transmit signal is still sent to the remote Megaplex.
The loopback signal path is shown in Figure 4-1.
Remote Digital Loopback (Remote Loop)
The remote digital loopback is performed at the receive output of the channel
receive path, by connecting the digital signal received from the main link to the
input of the channel digital transmit path.
When the loopback is activated, the digital receive signal remains is connected to
the input of the receive path, and is returned toward the remote end.
The loopback signal path is shown in Figure 4-2.