CSP-1750 and CSP-1756

Photo of CSP-1750

Photo of CSP-1756
CSP-1756, Photo Copyright © 2007, Richard Brisson. Used with permission.

DESCRIPTION OF CSP-1750, Call Sign Cipher

CSP-1750 is a call sign cipher used to encrypt the call signs and address groups used on radio circuits.

CSP-1750 is a little box, roughly 4"x2"x10" on a wire frame that tilt edit up to 45 degrees. There are four columns with chains behind the columns. The columns are labeled with A-Z, /, 0-9. A metal stick is inserted at the letter and it catches the internal chains. The stick is then pulled down and at the bottom of each column is a window that displays a number between 00 and 36. The four chains are pulled down 4 times and the values in the windows are then used to look up the resulting call sign in a book.

The knob on the left is used to "zeroize" or reset the device. The clips on the right are used to hold the stylus.

Please see the Operation Instructions for CSP-1750 and CSP-1756 for detailed information on these devices.


Instructions for Penelope Cryptosystem, Operation and Maintenance of CSP-1750 (KA-2) and CSP-1756 (KA-3), AMSP 295(B), February 1965.

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