Extended Line Feed Option: AI-7280
The default configuration for the AI-7280 is to have a line feed circuit that is capable of 72V maximum when in the on hook state and 72mA maximum when the line is terminated with a load. This suits a vast array of test conditions as the nominal line voltage found in most networks is 48 to 50 volts. However, it is still common enough to find standards which define much higher voltage and current test conditions. These test conditions ensure the device will operate not only at the nominal case but also over the entire range of loop feed conditions that can be found in the field. This option is especially suited to test environments that seek to show compliance with published standards.

The example below shows the AI-7280 set to sweep the line feed voltage from 0 to 105V while the resulting current through the load is measured. This provides a clear indication on the performance of the telephone or FXO load.

If the FXO limits the current over a specific value as is required in many ETSI specifications the results would look more like the following.

Another example shows the C-Message weighted noise measured as a function of loop current to verify the performance across a wide range of loop conditions. The noise level is better than -76 dBV ( C-message weighted) and varies by less than 1 dB vs Loop current.

Just as with the default limits the AI-E702 option allows the DC feed to be configured as either a constant voltage feed common with legacy equipment or as a constant current feed as is common in the newer central office and FXS designs. This flexibility ensures testing on the same topologies found in the network.