4RF Aprisa XE User Manual page 125

7. Select the DFXO Impedance
This option sets the DFXO line termination impedance and the hybrid balance impedance to the same
value.
Selection Description
600 Ω
Standard equipment impedance
600 Ω + 2.16 uF
Standard equipment impedance with low frequency roll-off
900 Ω
Typically used on loaded cable pairs
900 Ω + 2.16 uF
Typically used on loaded cable pairs with low frequency roll-off
TN12 Standard complex impedance for Australia
TBR21 Widely deployed complex impedance
BT3 Standard complex impedance for New Zealand
BT Network Standard complex impedance for UK
China Standard complex impedance for China
On a short line (< 100 metres), the selected impedance should match the impedance of the
exchange line card.
On a long line (> 1000 metres), the selected impedance should match the impedance of the
exchange line card as seen through the line.
If you are not sure what the expected impedance value should be, check with the exchange
equipment supplier.
8. Enable the DFXO Echo Canceller if required.
The DFXO Echo Canceller provides up to 64 ms of echo cancellation. This feature is only available on
Rev D (and later) DFXO cards.
Analogue data devices e.g. modems send a disable signal to disable any echo canceller in circuit while
it trains its own echo canceller. There are two possible disable signals. ITU G.164 specifies a disable
signal of a single 2100 Hz tone and ITU G.165 specifies a disable signal of 2100 Hz tone with phase
reversals every 450 ms.
Selection Description
Off No echo canceller operation.
On Echo canceller operational but without disabling.
Auto Disable Echo canceller operational with automatic disabling using ITU
G.164 G.164 2100 Hz tone.
Auto Disable Echo canceller operational with automatic disabling using ITU
G.165 G.165 2100 Hz tone with phase reversals every 450 ms.
Aprisa XE User Manual
Configuring the Traffic Interfaces | 123
Default
Default