As often the case, I recall wrong. I stand corrected. Dwight From: dkelvey at hotmail.com To: cctalk at classiccmp.org Subject: RE: 21MX proms (per request Date: Thu, 10 Sep 2015 12:09:39 -0700 Yep, looked it up. 2716 and 2732 used a pulsed Vpp( 2708 a well ). Beyond that they had a static Vpp and a PGM pin. Dwight