The PTL-1 is a Q-Sys accessory that provides an end-of-line 22 kHz impedance soak for 70/100V loudspeaker circuits. Used in combination with a QSC DataPort-equipped amplifier or CXD platform amplifier, the PTL-1 becomes a vital component for monitoring of a distributed loudspeaker line. Q-Sys monitors the integrity of a loudspeaker line by transmitting a 22 kHz pilot tone (outside the audible range of human hearing and undetectable amidst the program material) and continually sensing the impedance of the PTL-1 installed at the far end of the line.

A significant drop in impedance will indicate a short circuit in the line, while an impedance rise will indicate a break or other open-circuit fault. With each detected failure, Q-Sys can generate a time-stamped entry in its Event Log and can be programmed to trigger an alert message.