Looks like Digikey turned them into a special order item.I just checked my lab and for some reason I have 4 tubes of the ISD1420P. I have about 60 of them with a date code of 0009.
So I will make a Repeater-Builder list and NHRC-2 upgrade special. A never before seen offer! Send me a self addressed padded envelope, with some anti-static foam that will fit a 28 pin .6" wide dip along with the qty of chips you need and I will send you some. First come first serve. Matt Krick 3370 N. Mobile Rd. Golden Valley, AZ 86413 Please make your reservations on list as I do not want anyone to be eaten by the spam filter. I also have some ISD2575Ps, but I don't know of anything that uses them off the top of my head. I need to get some more PICs from NHRC my self. I have 2 controlers that are just sitting here.

