[cctalk] Signetics N8220B ??

Hi guys, I have 8 "new" Chips from Signetics, they are labeled: S7536 N8220B and on the backside between the pins "8220". Does anyone know what they do? My search with google and in the 1976 Signetics Date Manual (from Bitsavers) wasn't helpful... Thanx in advance, Holm -- Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe, Goethestrasse 15, 09569 Oederan, USt-Id: DE253710583 info(a)tsht.de Tel +49 37292 709778 Mobil: 0172 8790 741