Tally Genicom Matrix Printer Calculating Characters per Inch

7265 Programmer’s Manual 47

Calculating Characters per Inch

We show characters per inch at the default element widths and 0o/180o rotation f or each style in

the following chapter. All of our numbers ignore the quie t zones; you need to allow 1/2 inch per

symbol for the horizontal rotations.

Defining characters per inch for fixed-length codes is stra ightforward in that the start-stop and

center characters always take up the same portion of length of the symbol. The styles that have

center characters are all fixed-length.

For variable-length codes, net characters per inch depen ds on the number of data characters in

the symbol. The overhead imposed by start-stop characters is the same whether a symbol

represents 1 data character or 10, so the net cpi is greater f or longer symbols. We show the

overhead imposed by start-stop characters separately for th e variable length codes.

The default element widths are the narrowest that we recomm end. If you use wider element

widths and maintain a 3:1 ratio of wide elements to narrow el ements, then you can extrapolate

characters-per-inch for wider symbols. If you depart from the 3:1 ratio, then it's simpler for you to

print test symbols and derive formulae based on what you measure than it is for us to tell you how

to do the computation for each style.

One way to determine the combined length of start-stop c haracters for a variable-length symbol is

to print two symbols, one with twice as many data characters as the other. Measure the shorter

symbol and call this L1; measure the longer symbol and cal l this L2. The combined length of the

start-stop characters is:

d = (2 x L1) - L2

To summarize, when using our cpi figures to predict the le ngth of a symbol, remember:

• Allow for two quiet zones per symbol.

• For variable-length symbols, allow the combined start-stop character length for each symbol.

• If you use a check character, then allow for the check character.