The CSP 1515 is a machine which produces additives applicable
to messages on teletype tape. For a given setting of the
machine current enters at five fixed input points and passes
through five wired wheels. Fifteen of the output points, in
five groups of three are wired to five relays. Each relay
is associated with one of the levels on the teletype tape.
If current reaches the relay the component appearing on the
message tape is reversed as it goes to the cipher tape, a
mark becoming a space or a space becoming a mark. If no cur-
rent reaches the relay, the component on the cipher tape will
be the same as the component on the message tape. In this
way, an additive modulo 2 is applied to each component of the
message tape and incidentally decipherment is the same opera-
tion as enciphermente
Five wheels of standard 26 wire type are used at a time.
They are chosen from a set of ten and may be inserted straight
or in reverse, permitting 967,680 wheel orders. Any one of
the five wheels may be designated as the fast wheel, stepping
every time. Any other may be made the middle, stepping every
twenty-six letters, and a third made the slow wheel, stepping
once every 676 times. The other two wheels step in a manner
dependent on the additive produced. When the first three
relays all receive current simultaneously, the fourth wheel
steps and when the last two relays both receive current, the
fifth wheel steps. There are no settable rings and no stecker.
A grenade run could be made on a known wheel order, though
several runs would be needed to cover the 120 different mo-
tions. No other existing equipment appears to be applicable.