To monitor the state of the air filter, RMF Systems offers a Filter Minder (vacuum switch). The filter minder is a combination graduated indicator and switch (N/O), a yellow indicator moves up in the window and locks at the highest air filter restriction. When it reaches the red zone, or highest recommended restriction, it closes a contact and can send a signal to the filter warning light. The locked position at highest restriction must be reset manually. The filter minder can be fitted to a variety of the RMF Mounting or Adaptor Plates.