Six transmitters are table tape transmitters. They read tables of numbers when directed to. A table tape can be as long as 100 feet and will hold numbers at the rate of 1 inch per number, so that about 1200 numbers of seven decimal digits can be stored on a table tape.

When we look up a number in a table, such as the following,

2½33½ ···
1 1.02500 1.03000 1.03500
2 1.050631.060901.07123
3 1.076891.09273 ···
4 1.10381······
5 1.13141···
6 1.15969
7 ···
8 ···
9 ···
10
··· ···

we look along the top and down the side until we find the column and row of the number we are looking for. These are called the arguments of the tabular value that we are looking for ([see Supplement 2]). Now when we put this table on a tape to go into the Bell Laboratories machine, we write it all on one line, one figure after another, and we punch it as follows:

2-½ 1-5 1.02500 1.05063 1.07689 1.10381 1.13141
6-10 1.15969 ··· 11-15 ··· ··· ··· 3 1-5
1.03000 1.06090 ··· ··· 3½ 1-5 1.03500 ···

You will notice that the column labels 2½, 3, 3½ have been put on the tape, each in front of the group of numbers they apply to. The row labels 1 to 5, 6 to 10, ··· have also been put on the tape, each in front of the group of numbers they apply to. The appropriate column and row numbers, or arguments, must be put often on every table tape, so that it is easy for the machine to tell what part of the table tape it is reading.

In the Bell Laboratories machine, we do not need to put equal blocks of arguments like 1-5, 6-10 ··· on the table tape. Instead we can put individual arguments like 1, 2, 3, 4 ···, or, if we wish, we can use blocks of different sizes, like 1-3, 4-15, 16-30···. For some tables, such as income tax tables, it is very useful to have varying-sized blocks of arguments. The machine, when hunting for a certain value in the table, makes a comparison at each block of arguments.

The machine needs about 6 seconds to search a foot of tape. If we want to set up a table economically, therefore, we need to consider the average length of time needed for searching.

Fig. 1. Scheme of a recorder.