Artifact Details


WWVB Clock main unit

Catalog Number



Physical object




Spectracom Corporation

Place Manufactured


Identifying Numbers

Model number 8170
Other number 08 Time Zone
Other number 17.2 Path delay
Other number 21272 Property of US Government on back
Serial number 8170-0439


5 x 17 x 14 3/4 in.


This device is a radio clock intended to be read by computer. It was one of four built by Spectracom, Inc. in around 1981 for the Defense Advanced Research Projects Agency (DARPA) . In the years since then until the 1980s, it and its successors have provided basic computer network time synchronization for the ARPANET, NSFNET and eventually the entire Internet. This time function is now provided by a system based on Global Positioning System (GPS) satellites. [Optional text, used if device is on display and operating]:The time you see indicated here is accurate to within several milliseconds (thousandths of a second) of the national time standard kept at the U.S. Naval Observatory. There are three parts: A - Main unit B - Antenna C - 50' coaxial cable Relevant facts [courtesy of Professor David Mills]: The device is a radio clock intended to be read by computer. It was one of four built by Spectracom, Inc., circa 1981 for the Defense Advanced Research Agency. In the years since then, it and its brothers provided basic computer network time synchronization for the ARPANET, NSFNET and eventually the entire Internet through the late 1980s. Since then, their function has been largely replaced by newer satellite clocks synchronized to the Global Positioning System. Of the original four, two are in service here (largely for nostalgic reasons), one is held as cannibal and the last is within your grasp. The Model 8170 WWVB Synchronized Clock, which is the official name, is about the size of a VCR. If you can put up its antennna, about the size of a polo club, on the roof and run a wire, the clock will run within less than a millisecond of national time and present its findings on a LED display in real time. Museum visitors and staff can set their watches accordingly. Run a wire to a computer and you can set its time, too. The people that worked most closely with the thing were mostly nerds who designed and implemented the Internet protocols and architectures used today. These guys, and later the NSFNET Phase-I backbone, which used software of my design, synchronized their computer clocks in order to coordinate network experiments and monitoring data. The original four clocks synchronized four of the six switching nodes in the backbone, which then synchronized the remaining machines in the network using the Network Time Protocol, which I designed in the early 1980s and evolved in four versions since then. The NTP architecture and protocol is currently in use by over 100,000 hosts all over the world, with time provided by over 230 radio and satellite clocks like the 8170. More info, should you care to probe, is on the NTP site and my home page ...~mills. Note from donor [Basil Irwin, NCAR]: I just checked on the Spectracom clock that would be donated. It's still powered up at NCAR and seems to be in working condition as far as the front panel LED display is concerned, and it appears to be obtaining a correct time off of the radio. (Thus as part of the history of the clock, the last place the clock was used as a production network time source was at NCAR in 1997.) The operational capability of its computer interface is in doubt, which is why we're removing it. Even if it did work, you'd have to find an old system with an old operating system with an old device driver and old software to make it work. I would think just displaying the correct time would be a very nice attraction though. It does appear to display GMT, so conversion to local time could be shown in a caption. Other facts: Sicker on unit (loose) reads: "Clock #2 [S/N 8170-0439] Calibrated Oct 30, 81 - D. Cole. Possibly adjusted at factory since then. Best approximation to built-in delay is 14.4ms when used at ISI, the switch setting shoudl be: 19.1" ISI - USC Information Sciences Institute. U.S. Government sticker reads: "Property of U.S. Government 21272" [Unit has been been properly de-inventoried by David Mills, U of Delware.]


Fixed-application digital computer: other


Gift of Basil L. Irwin

Lot Number