3M™ Peltor™ Optime™ PTL earmuffs represent a transitional model from passive earmuffs to active protection earmuffs.
A built-in electronic filter in the right cup activates by push-button and transmits outside sounds up to 87 dB. The filter will remain on for a period of 30 seconds  and then automatically switches-off. If you want to prolong its functioning you have to push the button again. To end the function before the 30 second time period the user would simply push the button again.

These earmuffs allow communication in noisy environments without lifting a soundproof cup and without taking the earmuffs from the head. This greatly increases the efficiency of anti-noise protection.

SNR=29 H=30 M=27 L=21 *

Power source service life: 1 AA battery - 150 hours or 18.000 cycles of the push button.
Weight: 290 g.
TR CU 019/2011

* SNR – Single Number Rating, H – high frequency reduction, M – medium frequency reduction, L – low frequency reduction.