Abstract: Apparatus is disclosed for use with typewriters of the type having trip hammers and is adapted to receive combinations of electrical signals which uniquely define the respective characteristics and to decode the electrical signals to selectively activate the trip hammers of the typewriter. The apparatus has a number of coded plates located adjacent one another in general alignment, with each of the plates having a number of transverse slots at one edge thereof at predetermined positions. Lateral or longitudinal movement of the elongated plates between first and second positions in response to receiving appropriate electrical signals causes the slots to be either into or out of alignment with an activating member which effects triggering of the trip hammer of the typewriter. Any one of the coded plates having a slot in a nonaligned orientation will prevent activation of the particular hammer.

Abstract: Apparatus is disclosed for attachment to a standard typewriter for selectively actuating one or more of a plurality of magnetically actuated switches to provide unique electrical signals that can be recorded or otherwise used to transmit information. The information electrical signals are produced in response to actuation of the typewriter key and an opto-electronic switching circuit is utilized to prohibit the generation of the electrical signals unless and until a type head strikes the platen. Reed switches and actuating levers are provided for each of the unique keys of the typewriter so that signals identifying the corresponding character or function can be produced.