Sorry. SONY's not very good at specs on old items. All I found was a site where you can download the manual for $15 and change as a PDF. Obviously, ECM designates an electret condenser mic, and it is one of a series of one-point stereo mics, almost certainly battery powered. Beyond that, there isn't much out there. If it was a Shure or an AKG, you could get the specs on a 50 year-old mic. I'd try sending an email to support at SONY USA, and see if they send you anything. Good luck-Richie