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KW - 26
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KW - 26

Information : GENERAL

The KW-26 was used by U.S. /NATO intelligence services to provide point-to-point 100 wpm circuits for expeditious transmission of highly compartmented information. Only the keying material differed from that issued to operational units. Each circuit had a scheduled re-key time every 24 hours called BRAVO INDIA (BI), a process specific to the KW-26. It was used prior to HJ (HOTEL JULIET).

However, in the early 60's, most long haul communications were via radio propagation which was subject to many forms of interference both man made and natural. Since the receiving unit could only tolerate a bias distortion rate of about 25-26%, many circuits were constantly dropping synchronization, thereby necessitating many re-key/re-starts daily. Since most of the circuits were long haul and ciphony was not yet prevalent, the circuit stayed in the clear until a restart could be accomplished.

VARIANTS:

- First unit delivered in 1957 [1]

-A First version
-B Dual "ping-pong", manually synchronized. Used by the British on mutual US communications
circuits at 66 wpm. It used two Phase Indicator Lights on the receiver which flashed alternately.
-C Most common version. It had one Phase Indicator light on the receiver.
-D Last version.

- At one time the NSA Communications Center had 336 KW-26's in operation. [1]

RECEIVER vs TRANSMITTER DIFFERENCES

The KW-26 receiver and transmitter look nearly identical, however there were two differences. Ken Sutterfield explains " Transmitters did not have Phase Indicators, they had a transmit light. The "C version of the transmitter also had an alarm test switch located above the meter on the left side of the front panel. It was similar to the meter switch located below the meter".

The 'B version of the transmitter had the Alarm test switch mounted internally. Doug Eyre explains. It was on the A7 panel on the left side. We had to open the equipment to perform the alarm check. As I recall, the alarm switch was "hidden" because outsiders were not to know how many alarm positions there were (14, I think). We were supposed to check each position and clear the alarm with the switch. But the last position should not have been able to be cleared. Alarm checks were perfunctory at best".

KW-26A

kw26.jpg
KW-26 'A' Model. (Photo courtesy
www.ehistory.com . Used with permission)
Doug Eyre describes the photo. "This is just the receiver section (top) and its power supply (below). The transmitting unit, nearly identical in appearance, was usually mounted directly below the receiver. There are power meters, test switches and fuses located behind those covers on the receiver unit. I suspect they were for the prevention of TEMPEST. Power was applied by switches on the right side of the power supply in between the yellow lights. Control circuits sequenced the power in stages.

On the receiver unit, at the right side, there are two white-collared jacks. That is where the "roll around" TTY monitor was plugged in to. There are two black rotary switches. The one on the right was for plain, cipher local, and cipher remote. If you were in cipher local, the equipment only communicated with the roll around monitor. Once you put it in remote, then everything was operating normal"