KG84A (Tri-Tac)

The KG-84 family of equipment was a series of general purpose cryptographic devices intended to replace existing, aging equipment and satisfy emerging secure communications requirements. The 80 series family had no designator other than Tri-Tac which was a communications platform consisting of the TYC-39 (data) and TTC-39 (voice) systems. Both systems were comprised of two shelters.

KG84A's were general, high capacity key generators used to encrypt and decrypt teletypewriter and digital data in both tactical and fixed plant environments. It has four selectable traffic key slots, improved remote rekeying, and mandatory EIA-RS-449 control signed.  Data is processed at digital rates from 50 to 9,600 baud (non-synchronous), up to 32,000 Kb/sec using an internal clock. It can operate at data rates up to 64,000 Kb/sec using an external clock for synchronization and  is capable of operating in full duplex, half duplex, or simplex modes.  The KG-84A may be used in tactical, strategic, ship/air, and fixed plant environments. It was approved for use at all classification levels.

The KG-84C was a Dedicated Loop Encryption Device (DLED), and both the KG-84A and C variants were designated as General Purpose Telegraph Encryption Equipment (GPTEE). The KG-84A was primarily used for point-to-point encrypted communications via landline, microwave, and satellite systems. The KG-84C was an outgrowth of the Navy high frequency (HF) communications program and supports these needs. The KG-84A and KG-84C were devices that operated in simplex, half-duplex, or full-duplex modes. The KG-84C contains all of the KG-84 and KG-84A modes, and a variable update counter, improved HF performance, synchronous out-of-sync detection, asynchronous cipher text, plain text, bypass, and the European TELEX protocol. The KG-84 A/C is certified to handle data at all levels of security. It is a Controlled Cryptographic Item and is UNCLASSIFIED when unkeyed. Keyed KG-84 equipment assumes the classification level equal to that of the keying material used.

The TSEC/KG-84C demonstrated significant enhancements over the TSEC/KG-84A, particularly an improved high frequency capability, but remained cryptographically compatible with the TSEC/KG-84, TSEC/KG-84A and TSEC/KG-82. TSEC/KG-84A and TSEC/KG-84C will be referred to as the KG-84 throughout the remainder of this document.

KG-84 provided significant improvements in reliability, key variable distribution, and security over existing equipment. The incorporation of large-scale integration (LSI) technology allowed the KG-84 to realize a substantial reduction in size, weight, and power consumption requirements.

It accepted plain-text digital data from various input/output (I/0) devices or data adapters in either full duplex, half duplex, or simplex modes of operation. Input data may have been a continuous bit stream synchronized at various clock frequencies ranging from 50 bits per second (b/s) to 32,000 bits per second or asynchronous data in specified formats at various stepping rates from 50 bps to 9,600 bps. An optional mode timing system allowed a choice of operating from either an internal or external clock source. The external clock option allowed operation at any arbitrary data rate up to 64,000 bps. The KG-84 encrypted the plain-text data and performed additional processing operations, such as diphase modulation, if required by system configuration to produce cipher-text information optimized for transmission to, the interfacing external equipment. Conversely, the KG-84 accepted incoming cipher-text data, decrypted the data, and performed other processing operations to recover the plain-text data or message. The resulting plain-text information was sent to a compatible I/O device or data adapter.

Unkeyed KG-84 equipment and components were classified as Controlled Cryptographic Items (CCI). CCI items are unclassified but remain under the control of DCMS. The KG-84 end items and RGQ-84 PWA spares kits were centrally accounted for at DCMS by serial number per reference (a). Keyed CCI equipment assumed a classification level equal to that of the keying material and was safeguarded per the provisions of reference. A security clearance was not required for viewing of or access to unkeyed KG-84 equipment and components.


For training of maintenance personal, no specific Military Occupational Specialty (MOS) was designated for the KG-84 operator. Formal operator training was limited to orientation and familiarization with KG-84 equipment at the Marine Corps Communication - Electronics School (MCCES), Twentynine Palms, California for MOS's 2549 (Communication Center Chief) and 2591 (Operational Communication Chief) and the Communications Officer School, Marine Corps Combat Development Center (MCCDC), Quantico, Virginia.

Operator training at the unit level consisted of on-the-job training using the operator's manuals available to each unit receiving KG-84 equipment. Each command was responsible for maintaining an adequate level of qualified operator personnel.

Initial KG-84 maintenance training was provided by the Navy Cryptological Technical Maintenance School, Mare Island, California, and the Technical Training Center, Lackland Air Force Base, San Antonio, Texas.


TM 11-5810-309-10 Operator's Manual, Dedicated Loop Encryption Device, TSEC/KG-84A.

TM 11-5810-309-23 Organizational and Direct Support Maintenance, Dedicated Loop Encryption Device, TSEC/KG-84A.

TM 11-5810-308-24P Organizational, Direct Support and General Support Repair Parts and Special Tools List, Dedicated Loop Encryption Device, TSEC/KG-84A.

TM 11-5810-377-10 Operator's Manual, General Purpose Telegraphic Encryption Equipment, TSEC/KG-84C.

TM 11-5810-377-23 Unit and Intermediate Direct Support Maintenance, General Purpose Telegraphic Encryption Equipment, TSEC/KG-84C.

KAO-184()/TSEC Operating Instructions for TSEC/KG 84/KG-84A.

KAO-210()/TSEC Operating Instructions for TSEC/KG-84C.

KAM-410()/TSEC Limited Maintenance Manual for TSEC/ KG-84/KG-84A.

KAM-411()/TSEC Theory Textbook, TSEC/KG-84/KG-84A.

KAM-412()/TSEC Maintenance Troubleshooting Manual, TSEC/KG-84/KG-84A.

KAM-504()/TSEC Limited Maintenance Manual for TSEC/KG-84C.

KAM-505()/TSEC Maintenance Troubleshooting Manual, TSEC/KG-84C.

MI-07115B-35/2 Modification of the AN/TYC-5A(V) to accept TSEC/KG-84 COMSEC equipment.


The C-11828/U Remote Control Unit (RCU), P/N ON363501-501, was designed for use with the KG-84 family of equipment. The RCU provided the capability to remote front panel controls and indicator status displays up to 1,000 feet from the installed KG- 84 equipment. A Remote Indicator Unit (RIU) was developed by the NESSEC for shore applications where the full capabilities of the C-11828/U were not required.


Both the KG-84A and KG-84C have a built in wireline modem capability. In addition, there are two optional modems that may be installed internal to the KG-84A but not the KG-84C. These are the frequency shift key modem, PWA E-ENK and the Type 1 modem, PWA E-EWW. Either of these modems can be installed in the KG-84A by swapping the respective modem PWA with the black I/O PWA. Detailed installation instructions are included in the respective maintenance manuals. These modems were made available in 1990.

The KG-84A (left) and the KG-84C (right). (Photo courtesy of U.S.N. )

Physical Characteristics for both the  KG-84A and -84C

Height (in) - 7.8
Width (in) - 7.5
Depth (in) - 15
Weight (lb) - 23

Data Rate:

KG-84 -  up to 64 Kbps synchronous
KG-84A  - up to 256 Kbps

Operating Temperature: 0°C to 55°C

MTBF:  69,000 hours

Manufacturer: Pulse Engineering, Inc. and Bendix.

Unit cost:  $3,600  - no longer produced.

kg84a_complete1_s .jpg This view shows a KG-84 fully populated with circuit boards. Click on image to enlarge. (Photo via E-bay) 
kg84a_complete3_s.jpg Details of the logic cage lid. Click on image to enlarge. (Photo via E-bay) 
This view shows the markings over the KG-84A controls. (Photo courtesy Tony Snider of Virginia Beach, VA)
kg84pnl4.jpg kg84pnl1.jpg
This KG-84A photo shows the CCI label in place. From the battery install date, it looks like this unit was still in use in 1994. Photo courtesy Tony Snider of Virginia Beach, VA) Behind the KG-84A front panel.  (Photo courtesy Tony Snider of Virginia Beach, VA)

Closeup of  Functions and strapping placard for KG-84A. (Photo via E-bay)
Rear view of KG84A
All photos in this table via E-bay

KG-84 interface assembly still in the original packaging. (Photo via E-bay)
Rear view of interface. (Photo via E-bay)

This was the ST-2000 secure workstation. Included was the KG-84A which could encrypt record, data and voice communications. Optionally available were TEMPEST-accredited or non-TEMPEST component sub-systems. Options included secure facsimile, secure voice , high speed printers and modems. (All photos courtesy of Bendix/Allied Signal Technologies) 

kg84_acc_fill_device.jpg kg84_acc_cau.jpg
Fill Device - This key fill device provided for electronic insertion of the encryption key into the KG-84A. Crypto Ancillary Unit (CAU) -  A TEMPEST-accredited device which provided out-of-sync detection, resynchronization and verification of up to two KG-84A crypto units.
kg84_acc_fpa.jpg kg84_acc_counter.jpg
Fixed Plant Adapter (FPA) - TEMPEST-accredited device for mounting up to two KG-84A devices in a standard 19" equipment rack. It Included shielded interconnecting cables and mating crypto connectors. Update Counter - This device was used for detection, counting and display of successful variable update operations of up to two KG-84A crypto units. It was  designed to mount into the  FPA with KG-84A.
kg84_acc_fax.jpg kg84_acc_phone.jpg
Securefax  - TEMPEST-accredited digital facsimile transceiver which interfaced with the KG-84A encryption device over voice grade telephone circuits. It operated with external modem at data rates of 2400 to 9600 bps. Digitized Voice System -  TEMPEST-accredited, portable digital telephone designed for use with the KG-84A to provide secure voice. It contained an internal 2400 bps. full duplex, dial-up modem or could  utilize an external modem up to 9600 bps. 
The table above illustrates the various KG84 equipment options. (All photos courtesy of Bendix/Allied Signal Technologies)

Also refer to the KG-84C document in this web page.

References and Sources:

1) US Navy COMSEC web page.
2) Marine Corps document  MCO 2040.8, C2CT-DT dated 7 Nov 1988.
4) KG84 Data Sheet (1987)  - Joe Tag, Kean University. < joseph.tag(at)>
5) Vins Simmons    vinsimmons(at)>

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Sept 2/12