{HEAD ~ a variable attenuator} connected to the self test amplifier via {TAIL ~ a mixer}, and the microprocessor to generate a testing signal based on input from the self test amplifier and the microprocessor 
connected via
{ HEAD ~ a variable attenuator } connected to the self test amplifier via { TAIL ~ a mixer } , and the microprocessor to generate a testing signal based on input from the self test amplifier and the microprocessor
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH