+-------+-------+-------+-------+
 This diagram shows      |       |       |       |       |
 the numbers of the      |  20   |   10  |   11  |   12  |
 keypad keys on VT52     |       |       |       |       |
 terminals for use in    +-------+-------+-------+-------+
 the DEFINE KEY          |       |       |       |       |
 command.                |   7   |   8   |   9   |   13  |
                         |       |       |       |       |
                         +-------+-------+-------+-------+
                         |       |       |       |       |
                         |   4   |   5   |   6   |   14  |
                         |       |       |       |       |
                         +-------+-------+-------+-------+
                         |       |       |       |       |
                         |   1   |   2   |   3   |   15  |
                         |       |       |       |       |
                         +-------+-------+-------+-------+
                         |               |       |       |
                         |       0       |   16  |   21  |
                         |               |       |       |
                         +---------------+-------+-------+