BTW, here's a preview of the 1a2 board I've been working on, the reason I needed the described 66 block.. a small electronics project gone out of control
Basically a "single board" KSU. Basically does what a 511a KSU does, but small, light, and with some added features.
Makes it "easy" to hook up a bunch of 1a2 phones for use with the usual features (Hold, call transfer, lamps, intercom, bells, buzzers, programmable ringing). Just add a 12v supply, some 1a2 phones, and some US style POTS compatible lines.
Still working on finishing touches, but it's pretty close to being done. Will probably make a webpage for it to "open source" the schematics, circuit description, board layout, manual.
Questions welcome.