2. Turn the power switch on.
3. Find the two metal posts on the circuit board labelled TP1 and TP2. These are testing points.
4. Connect a voltmeter across TP1 and TP2 (Positive on TP1 and Negative on TP2). (You can use a multimeter set to a low DC volts range.)
5. Blow the horn with your usual strongest breath, and adjust VR2 so that the meter shows 2.35 - 2.40 volts.
6. Stop blowing and adjust VR1 so that the meter shows 0.55 - 0.60 volts with no breath.
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