EFData Modem Processor Board PL/3970 this board comes from our spider infested basement. It is almost impossible to find additional information and so much of this description is guesswork.
Based on the format of the board we assume that it belongs to the SDM 6000/9000 series of modems that have separate cards for modulation and demodulation. The main board has two daughter boards, PL/4124 and PL/4401-32.
Our long standing, and I should say considerable skill in this area, allows us to identify the board as a de-modulator (that’s because it says so on the board)
We cant test it, but if it doesn’t work, you may return it within 30 days for a refund.