in good working condition. 

From Peavey:

The Q215FX offers two channels with 15 bands of 2/3 octave filters featuring superior constant “Q” devices. Each channel has Peavey's exclusive FLS™ Feedback Locating System that consists of LED indicators above the frequency bands to identify the presence of a high energy signal (usually feedback). This sophisticated feedback detector system will allow you to quickly identify and remove feedback. It works like this: when the feedback detection circuit detects the frequency band with the most energy, it causes the LED above the associated frequency band to illuminate. By moving the fader downward for that band, the likelihood of feedback is reduced/eliminated. Most use the Q™215FX in one of two ways: 1. To catch and reduce/eliminate feedback “on-the-fly” during a performance. 2. To determine frequency bands that are susceptible to feedback BEFORE the performance, eliminating them in advance. How do you do this? After the system is set up, slowly bring up the microphone levels. As they start to feedback, note the LED activity on the Q™215FX feedback bands. Move the faders to decrease the “identified” bands. Now you have eliminated a high percentage of potential feedback problems before the performance even begins!