Last July (July 2014) Tim Mallory of First Texas made a post on a Facebook page. First Texas is the parent company of Fisher, the well known detector manufacturer. Fisher used to make a pulse induction diving detector, the Impulse, but it has been discontinued. Fisher stands out as a company with strong VLF prospecting detectors but also as the only "Big 5" manufacturer without a PI detector of any sort in the lineup. 2019 Edit - Announced as Fisher Impulse AQ Fisher was also a leader