Click for homepage
← DS-102
DS-101   EKMS 603
Common fill interface protocol

DS-101 is the current interface standard for electronic transfer devices, or fill units, developed and endorsed by the US National Security Agency. It superceedes the older DS-102 standard and is supported by nearly all modern radio sets and encryption devices, although most equipment is still backward compatible with DS-102. DS-101 is supported by fill devices like the AN/CYZ-10.

DS-101 is described in the EKMS 603 standard, but unfortunately this standard is not publicly available. It is known however, that DS-101 is an asynchronous serial protocol running at 64 kb/s. It is also known that it uses the HDLC protocol.

The physical interface is specified as RS-485, but RS-232D versions are known to exist as well, which is useful when PCs are involved. In most cases, devices that support newer DS101 – with an anynchronous RS485/RS232 interface – still support the older synchronous interface and are therefore backward compatible with DS102.
AN/CYZ-10 in operation

Unlike the DS-102 standard — which can only transfer cryptographic keys and frequency hopping tables — DS-101 can differentiate between various key and data types by using data tagging. As a result, DS-101 can also be used for distributing firmware and cryptographic algorithm updates.

PLEASE HELP — At present, not much is known about DS-101, EKMS-603 and the underlying data structure. You can help us to expand this page by providing additional information about transfer devices that use DS-101, supported radios, supported encryption devices, and the underlying data structures and protocols.

 Contact us
DS-101 fill devices on this website
AN/CYZ-10 Data Transfer Device
Thales DTD-II - Data Transfer Device 2
DS-101 compatible devices on this website
Narrow-band Voice and Data Terminal
KG-40A Replenishment
For connection between the FILL unit, and a radio or encryption device, most devices used a standard U-229 connector. In many cases, this connector is shared with the audio functions of a military radio, for example for the connection of a handset. This connector has 5 or 6 spring-loaded contacts, and is available in a male and female variant, as shown in the diagram below.

Although each variant has its own specific type number, they are often referred to as U-229/U, or simply U-229, after the female 5-pin cable part. The table below shows the pinout of this connector for the DS-101 standard. On encryption devices this connector is commonly used exclusively for the FILL function, but on radio sets it is often shared with the audio functions.

Pin Name Description Note
A GND Ground (common wire)  
B RTS Request to Send  
C RX Data out of radio or crypto device  
D TX Fill data into radio or crypto device  
E CTS Clear to Send  
F - -  
  • Name
  • Standard
  • Creator
  • Interface
    RS485 and/or RS232D
  • Type
  • Baudrate
    64 kb/s
  • Handshake
  • Protocol
DS-101 compatible fill devices
  1. Wikipedia, High-Level Data Link Control
    Visited 24 April 2024.
Further information
Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
Crypto Museum. Created: Sunday 11 February 2018. Last changed: Wednesday, 24 April 2024 - 08:38 CET.
Click for homepage