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