In a pile of stuff: ===Collins=== NO. 673 0280 00 Band Pass Filter Class A Grade 1 142-158 CPS Pass Band 0-DC With a nice picture of a transformer-coupled filter layout on the front. 30 VRMS 8000 ohms on one side, 1500 ohms on the other side. Ok, why would anyone need a filter for 142-158 hertz? Just curious. Chris w0ep