LED/sound alarm combination with acknowledgment function by tapping – Series 450. Unique acknowledgment function: By lightly tapping the front, the acoustic signal can be turned off, leaving only the visual signal active to indicate the malfunction. Permanent LED light with an additional continuous tone. Acoustic signal can be deactivated by lightly tapping the front. Lifespan of up to 50,000 hours. Potential-free output for transmitting the acknowledgment to the control unit. Positive and negative logic possible. Tone frequency 3 kHz. Panel mounting for Ø 22.5 mm (Mzz x 1.5 mm) with anti-rotation protection.