Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!wuarchive!uunet!pilchuck!ssc!tad From: tad@ssc.UUCP (Tad Cook) Newsgroups: sci.electronics Subject: Re: Questions about cordless phones Summary: cordless fone freqs Message-ID: <716@ssc.UUCP> Date: 31 Dec 90 04:56:31 GMT References: <52@bootsie.UUCP> Organization: very little Lines: 76 In article <52@bootsie.UUCP>, olson@bootsie.UUCP (Eric Olson) writes: > I've got a few simple questions about cordless phones: > > 1. About 5 years ago, they started selling "new freqency" phones. > What was new, compared to the old phones? The old phones used several frequencies around 1.7 MHz for the base unit to transmit to the handset. They used channels around 49 MHz to go from the handset to the base. The 1.7 Mhz band was phased out, and now the base units operate at 46 MHz. > > 2. What frequencies are used by modern ("new frequency") phones? > AM or FM? Sidebands? Are they all exactly the same frequency, > or do some have different or multiple frequencies? The MODE (which has nothing to do with FREQUENCY) is FM. There are ten channels, and here they are: Base Handset 46.61 MHz 49.67 MHz 46.63 MHz 49.845 MHz 46.67 MHz 49.86 MHz 46.71 MHz 49.77 MHz 46.73 MHz 49.875 MHz 46.77 MHz 49.83 MHz 46.83 MHz 49.89 MHz 46.87 MHz 49.93 MHz 46.93 MHz 49.99 MHz 46.97 MHz 49.97 MHz If you listen with a VHF scanner radio, the best listening is on the base unit side, as this side transmits BOTH sides of the call. Several handset freqs, including 49.83, 49.845, 49.86, and I think 49.89 MHz are shared with kids walkie talkies, real CHEAP radio controlled toys, and those wireless "nursery monitors" used in baby's room. In fact, if you drive around any residential area with a scanner, there is a continuous carrier on 49.83 and 49.86 MHz from all the nursery monitors. > > 3. My roommate has an AT&T cordless phone with 3 "channels". I > guessed that they were upper SB, lower SB, and main band. He > claimed they were separate frequencies. What's the scoop? Yes, it uses three of the channel pairs on the list above. There are no tricks with upper and lower SSB. The FCC recently ruled that the manufacturers do not have to stick to the assigned channels anymore, as long as they are within the band, so things should get a LOT more chaotic soon. > > 4. (Not really a question) I know there are security codes sent > between base & handset, my questions don't pertain to those. The security code prevents folks from using another cordless phone to make calls on your base unit. It does nothing for voice privacy. Cordless phones are NOT private. It is legal to listen to them, and quite easy. > > Thanks for any info you might have! You're welcome! Tad Cook Seattle, WA Packet: KT7H @ N7HFZ.WA.USA.NA Phone: 206/527-4089 MCI Mail: 3288544 Telex: 6503288544 MCI UW USENET:...uw-beaver!sumax!amc-gw!ssc!tad or, tad@ssc.UUCP