by Doug Eyre

As I recall, the TSEC/KY-9 was a full-duplex voice encryption machine.  All KY-9's had to be HJ'ed (synchronized) at a specific time around the world because all of the command posts that had them had to be able to speak secure at the same time.

The unit itself was of a monster weight.  It was a large box about 3.5 feet high, about 2 feet wide and about 3 feet deep containing a safe and was painted in standard military gray.  It had a power indicator, safe dial and handle, and on/off button on the front.  All power and communications wiring was situated at the back of the unit.  The large on/off button on the front was mechanically linked to the on/off switch on the inside so that the operator could power the unit down without opening the safe door.  A telephone, which sat on the top of this cabinet, was used for performing the crypto changes. However, when the phone was hung up, the machine was "remoted" to the command post on the other side of the wall (in the particular location that I worked at).  This allowed us to make the HJ's without access to the command post itself.

Inside, the unit was built in four quadrants.  The top two quadrants each had a card reader.  The card readers were the same style/function as those on the KW-26 and KG-13 families of equipment.  However, these card readers were rotated 90 degrees clockwise from the orientation on the '13/26 panels.

There were a set of "railroad tracks" built into the case.  To troubleshoot, the door was opened, the tracks were lowered, and the entire guts could be rolled out on the tracks for maintenance purposes.  Each quadrant could be individually removed from the machine leaving nothing but the case and the tracks. The boards within the quadrants were solid state discreet components. Voice quality was "Donald Duck" at its best.  There was absolutely no possibility of voice recognition out of this unit.

As an anecdote, while attending class at Lackland AFB, TX for the TSEC/KY-9, our class of 6 students gutted the instructor's machine at the front of the room.  Since we had access to dry ice, we found an empty coffee can, filled it with water and then put in the dry ice and locked it inside the empty case.  When the instructor returned to class, he could not get the machine to turn on so he opened the case and a large cloud of vapor rolled out across the classroom floor.  Fortunately the instructor did have a sense of humor.  Oh, and where might be the guts of the machine?  They were in our laps as we sat at our tables.  The instructor told us he was going for a break and he would be back in 15 minutes and "his" machine had better be working when he got back.  It was!

USAF members with Air Force Specialty Code (AFSC) 306X0 carried a Special Experience Identifier (SEI) of 254 that indicated that they were trained/qualified on the TSEC/KY-9.  My diploma dated 29 June 1973 reads:


Our instructor was TSgt Wayne Sternar. I regret that I only have the last names of my classmates:  Jackson, Russo, Bradley, Poulus, and MacCaluso.  I would love to hear from any one of them.

On the last day of class, I received a call from my supervisor, MSgt Jack. B. Wilson informing me that the replacement for the KY-9 was approved.  I got home to Mt. Home AFB, ID where I worked with the KY-9 until December of 1973 when our KY-9 was replaced by the Narrow Band Subscriber Terminal (NBST)(TSEC/HY-2 with TSEC/KG-13).  So, as you can see, my relationship with the KY-9 was short lived.

KY-9 image courtesy NSA
Warner W. Johnston adds to the above. "I was trained on the KY-9 at Lackland AFB in early 1969. As I recall, it did not use any potted circuits and the predominant transistor in the device was the 2N404.  I also remember it is as full-duplex, but again I haven't seen one in over 40 years. There was a switch hook which changed it from non-secure to secure mode, again as I recall. My class at Lackland included AF, Navy and Army personnel.

I was Army, not AF, but went from Lackland to Ent for OJT before being sent to USHQ Europe where we had more O-7 and above than E-3 and below The Army designation for MOS was a post-pended T."

Dimensions: 43 in H x 23.25 in D x 30.5 in H
Weight: 565 pounds
Cost: $40,000

Click here for KY-9 data sheet.

Various 2N404 transistors. These were used in the KY-9 (Photo courtesy Transistor Museum)

Credits and Contributors:

1) Doug Eyre
3) Warner W. Johnston <warner(at)>
4) 2N404 photo courtesy

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Feb 27/15