I knew I had the Tally Model 420 manual somewhere, and amazingly it was where I thought I'd put it.... There are 2 versions : 24V and 48V. The way to tell them apart seems to be to measure the resistance of the coils -- 48V ones are 220 Ohm, 24V ones are 50 OHm (all should be the same in a given machine). FWIW, there's a recomended suppression circuit in the manual consisting of an RC series circuit in parallel with each coil. For 48V, use 10 Ohms and 0.5 uF (I guess 0.47uF is near enough), for 24V use 5 Ohms and 0.7uF (4.7 Ohms and 0.68uF?) The manuals says 'The escapment assmbiles for the capstan drive and perforator drive mecahnisms require dc pulses of 4.5 +/- 0.5 milliseconds duration at 48 or 24 +/- 10% volts according to customer requirements. One pulse must be supplied for each movement of the tape and for each character to be punched. Puchn pulese for all 8 channels are normally derived from a common pulse, but if individual pulse sources are used for each channel, all pulses for any individual character must be simultaneosus within +/- 0.5 millisecond'. It also claims it'll go up to 60cps, which gives the maximum repitition rate for these pulses. You can go as slowly as you like, it's entirely asynchronous (unlike, say, a BRPE, which can be a right pain to interface). The manual also says 'CAUTION: A steady curret of the rated voltage will burn out the coils.' I assume you know the machine runs in an oil sump, level to be kept between the min and max marks, The recomended oil is 'Light turbine oil viscosity 160 SSU. Texaco A R & O or equivalent'. You should alos lubricate the motor bearings twice yearly (Bardahl BOA30 or equivalent) and the folloing points every 500 houes : Bearing bushces in the capstan drive, reel drive and ideler (Bardahl BOA30), wipe each armature and pole face and put 1 or 2 drops of lubricant on the felt pads (Bardahl BPA30, do not overlubricate) and one drop of lubricant on each armature tip (silicone fluid 250cs, Dow Corning 200). Don't ask me where to get these lubricants.... Having built a PC04 (well, converted a PC05 into one...) I seem to remember that the DEC punch mechanism is a synchronous one. The motor runs all the time, turnign the camshaft, you get a pulse per revolution fro ma pickup head, and the interface then drives solenoids to operate the punch pins and feed mechanism based on that timing. Now whether if you fed a suitable clock into the inferface card, you'd get out pulses that could be used to drive the asynchronous Tally mechanism I don't know, but it seems like a starting point. Alas the manaul tells me that a mating connector is supplied with the machine. Not a lot of help... -tony