21 May 2000: Add message.
20 May 2000: Add messages.
18 May 2000: Add message on Pulse Code Modulation Unit.
18 May 2000
Information on "the pulse code modulation unit" would be appreciated. Send to jy@cryptome.org
[Commerce Business Daily: Posted in CBDNet on May 11, 2000] [Printed Issue Date: May 15, 2000] From the Commerce Business Daily Online via GPO Access [cbdnet.access.gpo.gov] PART: U.S. GOVERNMENT PROCUREMENTS SUBPART: SUPPLIES, EQUIPMENT AND MATERIAL CLASSCOD: 59--Electrical and Electronic Equipment Components OFFADD: Contracts Group, Bldg 588, Mail Stop 32, Naval Air Warfare Center Aircraft Division, Patuxent River, MD 20670-5304 SUBJECT: 59--ELECTRICAL AND ELECTRONIC COMPONENTS SOL N00421-00-Q-0314 DUE 060900 POC Betty Goddard, Contract Specialist,(301) 757-9719 DESC: This is a notice of intent to negotiate with Delmarva Engineering, 1203 West St. Ste F, Annapolis, MD on an other than full and open competitive basis to purchase 2 ea p/n SP6-68-006-02 encryption unit/data rate = 10 bps. This item must be compatible and interchangeable with existing equipment. The government intents to negotiate on a sole source basis with Delmarva Engineering; who is the only known source that can meet compatiblity with the pulse code modulation unit. Written requests for copies of Request for Quotation may be faxed to (301) 757-0200 to the attention of Betty Goddard. All responsible sources may submit a quotation which wil be considered by the agency. SEE NUMBER NOTE(S): 1 EMAILADD: goddardba@navair.navy.mil EMAILDESC: goddardba@navair.navy.mil CITE: (W-132 SN453699)
____________________
http://www.smartbiz.com/sbs/arts/wcs7.htm
ACRONYMS AND LONG-DISTANCE TERMINOLOGY
DON'T UNDERSTAND THEIR LANGUAGE?
By Wanda Crosier Swenson
[Excerpt]
ADPCM UNIT--Adaptive Differential Pulse Code Modulation Unit. An additional piece of equipment that can be connected to a T-1 trunk which can double the capacity of a T-1 to carry 48 voice conversations simultaneously. Not all long-distance companies offer this service. Reduces the cost of installing an additional T-1 once you have out- grown your 24-channel T-1, if your application will be used for voice channels only.
____________________
http://www.cis.ohio-state.edu/htbin/rfc/rfc1890.html
Network Working Group Audio-Video Transport Working Group
Request for Comments: 1890 H. Schulzrinne
Category: Standards Track GMD Fokus
January 1996
RTP Profile for Audio and Video Conferences with Minimal Control
[Excerpt]
4.4.12 PCMU. PCMU is specified in CCITT/ITU-T recommendation G.711. Audio data is encoded as eight bits per sample, after logarithmic scaling. Code to convert between linear and mu-law companded data is available in [6]. PCMU is the encoding used for the Internet media type audio/basic. A detailed description is given by Jayant and Noll [11].
[6] IMA Digital Audio Focus and Technical Working Groups, "Recommended practices for enhancing digital audio compatibility in multimedia systems (version 3.00)," tech. rep., Interactive Multimedia Association, Annapolis, Maryland, Oct. 1992.
[11] N. S. Jayant and P. Noll, Digital Coding of Waveforms--Principles and Applications to Speech and Video Englewood Cliffs, New Jersey: Prentice-Hall, 1984.
I'm not certain where the adpcm article is headed - as in a general description of the idea or a specific description this unit, but a fairly good description of the process with and without encryption may be found on:
http://www.ece.cmu.edu/~ee551/Old_projects/projects/s_96_3/final.html
and links therein. I suspect you were more interested in the particular unit. I tried the Delmarva ftp site and although they allow anonymous ftp, I did not have much luck tranferring any documents, though there are a number of documents on the site. You might have better luck if the source of my difficulty was due to location. Their site is:
ftp://ftp.delmarva.com
Try looking under /pub/scoggin. As I noted, I wasn't able to transfer anything, so I can't say whether or not this is of interest.
[Thanks to MDF.]
The term "pulse code modulation" just means a bunch of 1/0 bits represented by pulses (ie, just about everything). The audio examples that you have appended to the page probably aren't relevant to the US Navy's request: audio systems, even highly compressed and carefully encoded ones, run at a rates much higher than the indicated 10 bits per second.
I'd suspect some kind of submarine communications system -- known to run at extremely low frequencies, and very low bit rates -- but the requesting agency is the "Naval Air Warfare Center, Aircraft Division"...
Quick searches on Delmarva Engineering reveal a few distributors for its products. Perhaps a catalog is available? There is also a domain-name "delmarva-eng.com". The web-page is obviously a place-holder..
[Thanks to anonymous.]
This device is to be used in submarines.
How can I say that?
OK, here it is :
There is no way radio waves can be transferred through very deep waters. The only thing that travels is sound.
The device is transmitting at 10 bit/s (10 hz) in water, only low frequency sounds can be transferred (around 100Hz is the max) to a significant distance to be captured by the microphones that everybody knows are floating around Guam and other island/... bases.
The PCM encoder uses the same coding as some remotes. The frequency is the same, the cyclic ratio differs.
For instance,
____
| |__| would be a 0, and
__
| |____| would be a 1
You can transmit then messages at 1 char per second. The encrypting device must be secure so that the message only appears as noise to unknowing ears.
Hope this helps.
[Thanks to WK.]
Knock yourself out...
http://www.fas.org/spp/civil/sts/newsref/sts-inst.html#sts-pcmmu
The same stuff from NASA
http://spaceflight.nasa.gov/shuttle/archives/sts-72/shutref/sts-inst.html#sts-pcmmuhttp://www.sieweb.com/Traindoc/documentation_catalog/glossary/test_P.htm#id_844
Hope it helps.
-WK
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"Communications without intelligence is noise;
Intelligence without communications is irrelevant."
Gen. Alfred. M. Gray,
USMC
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