"Roy J. Tellason" <rtellason at verizon.net> wrote: Hmm, like, say, an old cash register? This design is called "Volltastaturmaschine" in German (would translate to "complete keyboard machine"). They have a latching mechanism that holds in one button per column of keys (0-9, representing one digit of a number). When a calculation is initiated, the protruding shaft of the latched key acts as a stop for a toothed rack or similar device which is used to advance the wheels of the accumulator register by as many teeth as the corresponding digit says. There are also designs which involve an arrangement of levers positioning an intermediate gear along the axis of a stepped drum, for example the Badenia VA-17/VARE-17. The big advantage is that zeros need not be entered (to enter 100.00, you just press the "1" button in the fifth column from the right) and that operators could learn to "touch-type" on these keyboards, effectively entering all digits of a number in parallel and greatly reducing cycle times. Also, correction of mistypes is very fast and easy because you just have to latch the correct key in the respective column. I have a Diehl EVM series machine of that type, unfortunately the mechanism is about completely gummed up from old grease. Most mechanical and electromechanical ten-key adders contain a "pin carriage", which essentially is such a keyboard in miniature. A set of push rods connected to the ten keys is suspended above this construction; upon entry of a digit, the corresponding pin (sticking out through the top of the carriage after a clear) is pushed through (now sticking out at the bottom) and the carriage is advanced one position by an escapement mechanism. Ah...I suppose these were Odhner / Facit electromechanical pinwheel calculators, or at least a similar construction. I got one of those not very long ago and I'm very fond of it! A wealth of information about them is to be found on James Redin's Facit Page, http://www.xnumber.com/xnumber/cmisc_facit_page.htm The input register on those is a bank (or "drum") of pinwheel mechanisms which are actuated by the input keys - gears with an adjustable number of teeth, so to say. The "pins" are extended or retracted by rotating two parts of the gear against each other. For the calculation cycle, the adjustment is locked and the whole drum turns once, advancing the adjacent intermediate wheels (and thus the accumulator wheels) by the number of pins set. Machines with keyboard entry had to use a "split pinwheel" design in order to reduce the key travel needed, involving four pins and a sector with five more. 1 - 4 steps UP from the zero position extended 1 - 4 pins; 1 - 5 steps DOWN extended the sector AND 0 - 4 pins. Mechanical Bi-Quinary. Once a digit is set, the drum is advanced one step to the left and the next unset wheel is positioned in front of the setting mechanism. So long, -- Arno Kletzander www.iser.uni-erlangen.de Ist Ihr Browser Vista-kompatibel? Jetzt die neuesten Browser-Versionen downloaden: http://www.gmx.net/de/go/browser