What they are inferring by across R106 & R123 is exactly that.
Across the legs of two resistors that are attached to the emitters.
The middle point of the two resistors is the output.
They could have stated more clearly "Measure the voltage from Q13 Emitter to Q17 Emitter."
Across the legs of two resistors that are attached to the emitters.
The middle point of the two resistors is the output.
They could have stated more clearly "Measure the voltage from Q13 Emitter to Q17 Emitter."