of tapes. If one (say B) of the right-hand switches above the display is thrown,
the position counter shows how many sprocket-holes the start sign on B is behind
the start sign used as a start sign.
(f) Period Dials
These are above the display reading 0000 - 9999.
It they are set e.g. to 1271, as soon as the position counter reaches 1271
it returns to 0000 i.e. the reading is always the remainder on division by 1271.
(g) Split Position Counter
If one of the left-hand switches above the display is thrown the position
counter is split in two, each half working independently, reading up to 99. The
first two digits show the position of the tape selected by the left-hand switch.
The second two digits shown the position of the tape selected by the right-hand
Splitting splits the period dials also, e.g. if the dials are set to 4131,
the first two digits show the remainder on division by 41, the second two digits
show the remainder on division by 61. These may refer to the same or different
By convention the setting of one pattern relative to another is the place on
the latter against the 1st and not the 0th place on the former. Thus setting =
Rob reading + 1.
Stepping is effected on Robinson by using tapes of different lengths. If A
is m sprocket-holes longer than B, and the original setting is 01, then after a
revolution, A will return m sprocket-holes later than B, i.e. the 1st place on A
is opposite the (m+1)th place on B, and the setting of A relative to B is +m.
A is said to have moved forward relative to B.
(j) Repeat light
When the position counter returns to its original reading a repeat light