9. Line output XLR male socket Through this XLR male connector, the user can send out three built-in audio test signals: pink noise,1k Hz tone, and polarity signal. The output level is balanced -10dBu under 6DV power supply. 11. Contrast control By adjusting this control, the user can obtain better resolution from LCD when 10. Line input XLR female socket This port allows you to send balanced Line-level input to PAA2 via an XLR jack. This signal input allows you to measure line-level in dBu, dBV or AC voltage for balanced, unbalanced signal, or to check the phase of the input signal. Do not send DC voltage via this connector into PAA2, it will cause permanent damage to the unit. 12. Power lock Set this switch to the � ON� position before turning on PAA2. Set to the � OFF� position to prevent accidental powering of the PAA2 when the unit is not in use. It is recommended to set this switch off when you will not be using PAA2 for a long time. needed.