Paradise Datacom P300 Series Installation & Operating Handbook page 125

Options displayed on the second screen include all of the above, plus:
The data is looped back after the Drop mux, through the Doppler buffer, back
into the Insert mux providing a local loop only. The Tx data continues to be
transmitted and the Rx data from the satellite is ignored. If Drop/Insert
baseband processing is not active, this loops the data at the output of the
baseband block (ie it works even if Drop/Insert is not active). ESC & Aux
channel data is NOT looped.
The data is looped after the Framer back into the Deframer providing a local
loop only. The Tx data continues to be transmitted and the Rx data from the
satellite is ignored. ESC & Aux channel data (which is present in the data
stream at the Framer output) is also looped
The data is looped after the Reed-Solomon Encoder / interleaver back into the
RS Deinterleaver / decoder providing a local loop only. The Tx data continues
to be transmitted and the Rx data from the satellite is ignored. ESC & Aux
channel data (which is present in the data stream at the RS codec) is also
looped
From the terrestrial port towards the IF ports the loopbacks in the following order test more and more
circuitry: Interface, Drop/Insert, Framer, Reed-Solomon, FEC, IF.
This provides a loop of the Rx data after the deframer back into the framer. Tx
input data is ignored, Rx traffic continues as normal. Incoming ESC & Aux
channel data is not looped back to the remote site.
P300H P300 Series Modem Installation and Operating Handbook Page 125