Otherwise known as the "Glass Teletype", this seemed to be the video terminal of choice in the early days of computing for those who owned computers that required an external display or terminal: Altair, IMSAI, most notably. But a million others also. The ADM-3 allowed users the peace and quiet that users of the ASR-33 could not get without a really good set of earplugs!

I have two of these; An ADM-3 and an ADM-3A. The 3A differs most noticeably in that it included cursor controls. Both of my terminals have the lowercase option installed, but neither have the cool graphics add-on that was available. 

Neither of my ADM-3 terminals are in need of my famous tear-down restoration, but they both could use a little cleaning and paint touch up. I have recently cleaned the pots and adjusted the CRT controls in them, and they work just fine for now, old age not withstanding. 

Lear Siegler must have made ten million of these things, I have seen them everywhere. I did some work in Hawaii a few years ago at several Hawaiian-Tel central office locations, and they were still using a few of these.