TC-850; manufactured by Gretag AG, Regensdorf.

• Principle: Offline ciphering system
• Operation modes:

• Mains operation: 100, 120, 140, 200, 220, 240 V AC

• 590 x 545 x 280 mm, 37.4 kg (in box 655 x 625 x 310 mm, 51 kg)

• Accessories bag with power cable, 13 mm silk colour ribbon, box with spare parts

The TC-850 is a ciphering device for offline encryption. It was developed by Gretag in 1973/5 as the successor to the KFF58 and, unlike the KFF, no longer worked with the 14-segment code of the ETK, but could process the Baudot code used in standard teleprinters.

The set itself, like the sub-unit of the KFF, was not classified (but could at most be used as an electric typewriter with a punched tape reader), only the cipher unit needed to kept secret. The cipher unit is inserted into the back of the machine under the paper roll from above, the cipher unit is locked with the key in the 90° position and the system is ready for use.

With the main switch ON, the set is connected to the mains and the motors of the paper tape punch and paper tape reader start up.

The desired action is selected with the operating mode switch: in the REPRODUCE position, text can be sent from the paper tape reader to the page printer or the paper tape punch. In this position, the set is in CLEAR mode.

With the control command SSSSS the basic key can be entered via the keypad or the punched tape reader and is stored in one of the two memory locations.

With the command HHHHH transition to crypto mode is made, the set first automatically produces an additional key (encryption key) and then switches to the crypto operating state.

If a basic key has been entered and a crypto transition has been triggered with the HHHHHH command, the set switches to the Decrypt state after an additional key has been entered. The ciphertext entered via the keypad or the punched tape reader is decrypted and printed out on the sheet printer (if the SHEET PRINTER switch and OUTPUT position are set) or a paper tape is punched.

The TC-850 is built entirely using semiconductor technology.

The TC-850 was developed by Gretag AG, Regensdorf ZH, around 1973/5 and manufactured until 1977.

From the mid-1970s, the TC-850 was used for offline ciphering in the army command and also in embassy radio.

• The TC-850 ciphering device, Regl 58.112d, 1986

• TC-850 on www.cryptomuseum.com