R1 R2 R3 R4 R5, must be plugged or switched in the usual way. The
provision for them is less generous than for ordinary impulses. On the Q panel
they have two switches each in the upper part, one switch each in the lower part.
On the plug panel they have two jacks each: these jacks are part of Q and
are controlled by the main Q selecting switches.
(e) R1 R2 R3 R4 R5 : Relation to the Five Counters. (regrettably obscure.)
R1 R2 R3 R4 R5 may of course be switched or plugged into the counters in
any order; but Colossus cannot recognise this and therefore always prints the
setting. for a batch of five scores in the same order, viz backwards (e.g. 11, 10,
09, 08, 07).
The counters print in the order 1, 2, 3, 4, 5, and therefore if each
setting is to be printed opposite the appropriate score, the settings in the five
counters must likewise run backwards. (e.g. 11 in 1, 10 in 2, 9 in 3 , 8 in 4, 7
The settings corresponding to R1 R2 R3 R4 R5 also run back wards (R1 is
resent, R2 one back etc.) and therefore, finally R1 is switched to counter 1 etc.
It may sometimes be profitable to put R1 R2 R3 R4 R5 into the counters in
reverse order ( e.g. in rectangling).
(f) Manner of stepping
The wheel on multiple test can step either fast or slow [53D (c)] but in
either ease it steps five positions at a time, for obvious reasons. The batches
of five settings are not arbitrary but must belong to the sequence 02-06, 07-11,
12-16 ........ ending with the batch whose present position is O1 (e.g. X1
ends with 38-01). 1
(g) Multiple Testable wheels.
Multiple testing is provided for all wheels except Mu61 Xs , PSIs were added later
and have not been fitted to all colossi. Mu37 has its own switch: the others are
in pairs, each pair sharing a three-way switch, viz X1 , X2 ; X3 , X4 ; PSI1 ,
PSI2 ; PSI3 , PSI4 ; X5 , PSI5.
(h) Mu 37
Multiple testing on Mu 37 has some special features. It can be used only
for motor runs in which a count is made against motor = ., or motor = x. It
cannot be used for motorizing the psis.
The Mu37 multiple test switch, not only puts the wheel on multiple test,
but also puts Mu 37 alone into the switches R1 R2 R3 R4 R5 on the Q panel, where
it can be switched in the normal manner. (commonly Mu37' = ., but sometimes M37 +
Delta-D12 = . ). The effect of these switches is not modified by the limitation
determiner switches: they always represent the basic motor. For a total motor run
what is required is BM = . and lim = X. BM = . is imposed by these R switches.
Lim = x is imposed by the TM switch on the Q panel, the limitation determiner
switches being thrown to BM c/o and the appropriate limitation.