User's Manual

Table Of Contents

EX7100 Technical Manual – Monitoring and Diagnostics

4.5.3 Analogue Loopbacks

The six channel telephone version of the EX7100 is equipped with the ability to loop back

the audio on each of the six analogue lines. This function is done within the digital audio

processing section of the line interface card and therefore is transparent to the interface

configuration (2-wire or 4-wire+E&M).

Figure 4.4: Analogue Loopback Configurations

Local Loopback

Each channel may be put into local loopback mode from the front panel of the EX7100

terminal. In this mode, the transmit audio (into the EX7100 terminal) is looped back to the

received audio (out of the terminal), within the DSLAC (Dual Subscriber Line Audio

Circuit) device.

The user is now able to send an analogue signal into the radio and monitor it across the

same line (using a suitable test instrument with built in hybrid network). It is possible to

perform a similar test using a standard telephone connected to the line, but due to echo

cancellation effects, the received audio will sound distorted.

This feature enables a technician to confirm that the EX7100 line interface circuitry is

operating correctly.

Remote Loopback

Each analogue channel may be put into remote loopback mode from the front panel of the

EX7100. In this mode, the received audio from the remote terminal is looped back to the

transmit audio path.

From the remote terminal, a technician is able to send a signal down the line and monitor

it from the same location (using suitable test equipment with built in hybrid network).

DSLAC

LOCAL

LOOPBACK

LINE 1…6

DSLAC

REMOTE

LOOPBACK

LINE 1…6

DSPs