Other ideas,such as the electric pen, looked promis-ing, at least at first, judging from com-ments in the library press in 1877 and1879. The pen's story proves that inven-tions must not only serve a general need,they must adapt to the specific require-ments of libraries and conform withother existing technologies. Invented byThomas Alva Edison and patented in1876, the electric pen was a writing in-strument that used electromagnets and asmall storage battery. The actual pen,connected by wire to the power source,resembled a sewing needle; it producedsmall punctures in the form of letters andnumbers, and when an inked roller waspassed over the resulting stencil plate,legible copies could be made.