The latter however may be plugged via "Special Facilities". Note that this
forbids plugging direct from tapes to switch panel.
Subject to the above rules ( and some minor restrictions in the ordinary
addition fields) any jack may be plugged to any other. No jacks in the plug panel
ate permanently linked except the columns of the addition fields (ordinary and
(b) Pulses from Tapes
The arrangement is obvious from the picture.
The upper row is one forward on the tape.
The lower row is present position on the tape.
(c) Ordinary addition fields
Pulses (one or more) from tapes, plugged into input jacks in any column,
appear added together in both the output jacks of that column. For technical
reasons there are certain restrictions on the use of these fields. Each of the
left-hand five columns has two pairs of input jacks (upper and lower). Each of
the right-hand five columns has a single pair of input jacks. Impulses plugged
into the two jacks of a pair must come from the same tape. If there is only one
impulse in a pair it should be in the upper jack of the pair. Impulses from
different tapes can be added only in the five right-hand columns (or in the
special addition field). Each column of the addition field has two output jacks
from which the impulse may be plugged directly to the switchboard or to some
(d) Special Facilities
These are special addition, Permanent cross, one back and two back.
(e) Special addition field
This is exactly the same as a Colossus addition field e.g.
Note: other columns in the addition field are unaffected by this and can be used
(f) Permanent Cross.
The e is a column of jacks to the left of the special addition field: each
of them bears a permanent cross, which can be added, in the special addition
field, to any impulse. This is useful for making an impulse equal a cross when
using "direct plugging".
(g) One back and two back
There are five jacks at the right of the addition field