chain printer speed?

On 6/13/2006 at 12:22 PM Jules Richardson wrote: It depended entirely on what was being printed. There were worst-and-best case patterns. Consider the way a chain printer worked. You have a spinning chain, a wide ribbon, the paper and (usually about 132) hammers all making a sandwich. When a character in the chain is at the right position, the hammer at that position fires and bangs the paper against the ribbon backed by the type slug. Now, if the pattern being printed matches the order of characters on the chain (or the non-matching characters are spaces), you're all done and the paper advances. If not, then the paper has to wait until the proper characters come around to their respective positions. Clearly, the number of different characters in the chain is going to affect how many times they can be repeated in the chain; a chain containing lower-case characters in addition to uppercase is going to, on the average, print more slowly than a chain with just uppercase. Similarly, the manufacturer may have decided that some characters are so rarely used that they merit only one or two occurrences, while more frequently-used characters merit more frequent repetitions. Ordering of the characters on the chain also matters; placing a "U" next to a "Q" is a good idea. Most manufacturers give a number based on the average printing speed of a printer and 1500 LPM was about par for the high-speed models with "easy" lines going considerably faster.. But with the wrong type chain/train and pathological data, speed can drop as low as 60 LPM or so. Other factors could reduce printing speed, such as carriage control--when we printed documentation, we bolded characters by overstriking, essentially forcing the printer to print the same line 2 or 3 times. If you think about it, the chain/train printer is a perfect example of early parallel processing, although it was rarely stated as such. Cheers, Chuck