wn9nbt@ecn-ee.UUCP (08/22/84)
#R:ihuxf:-235700:ecn-ee:14900007:000:228 ecn-ee!wn9nbt Aug 21 13:33:00 1984 Anyone know the coding method they use ? I hope not the old balanced modulator scheme that a lot of police departments use. I've never listened to them, I'm just curious how they work... .....Dave Chasey -- pur-ee!wn9nbt
lauren@vortex.UUCP (Lauren Weinstein) (08/22/84)
Most of the new systems feed digitized audio through DES chips, and thus are "relatively" secure. How secure in REALITY depends on how far you trust DES. --Lauren--
jhs@Mitre-Bedford@sri-unix.UUCP (08/23/84)
The White House voice privacy radios are probably from Motorola. If so, they use 12 Kbps "CVSD" or Continuously Variable Slope Delta Modulation, with a DES-based encryption algorithm which Motorola has implemented in custom CMOS for this purpose. Or it may be a Motorola proprietary algorithm, as they have done some in-house work on other approaches to commercial encryption. In any case, it is NOT just a frequency inverter. 73, de W3IKG
piety@hplabs.UUCP (Bob Piety) (08/24/84)
Spread Spectrum communications could be used. Even if one were close enough to the transmitter to detect RF, it would just sound like static on an ordinary receiver. Most of the time, the signal would be substantially below the noise-- again, static received. --Spread Spectrum on 2M-- Bob (KG6HV)
parnass@ihuxf.UUCP (Bob Parnass, AJ9S) (08/29/84)
It's not spread spectrum. It's Motorola's Digital Voice Privacy (DVP), with the DES option no doubt. You can read about it in a DVP Mitrek manual, available for a buck or so at your local hamfest. -- =============================================================================== Bob Parnass, Bell Telephone Laboratories - ihnp4!ihuxf!parnass - (312)979-5414