JAJZ801@calstate.bitnet (01/05/91)
The latest issue of the DaMark catalog has a pair of "wireless phone jacks" by PHONEX. Actually they use household wiring. Does anyone know anything about the reliability of these things, their safety when used with faxes, modems, and other electronic phone equipment, and how much noise they can be expected to introduce into the call ? Jeff Sicherman
dave@westmark.westmark.com (Dave Levenson) (01/07/91)
In article <15796@accuvax.nwu.edu>, JAJZ801@calstate.bitnet writes: > The latest issue of the DaMark catalog has a pair of "wireless phone > jacks" by PHONEX. Actually they use household wiring. Does anyone know > anything about the reliability of these things, their safety when used > with faxes, modems, and other electronic phone equipment, and how much > noise they can be expected to introduce into the call ? Jeff identifies some valid concerns about these devices. I would like to add another: security. For some years, there has been home intercom and lighting-control equipment on the market that uses low-level RF to send audio or signaling information over your power lines. The RF signal used by these devices is conducted primarily by the power wire. There is also some radiation of this signal into the air. A nearby receiver, even if not connected directly to the power line, can probably intercept the information. A nearby transmitter, perhaps part of another, similar, system can radiate into the power line, and thereby interfere with the system. The RF is mostly blocked by the step-down transformer that feeds your house. If there are several houses fed from the same transformer (as is usually the case) these systems can easily communicate between these nearby houses. For this reason, there are a dozen or so channels available. Neighbors must reach an agreement on who uses which channels. In a large appartment building, there is typically a large transformer feeding the entire building. There are probably more appartments on each phase of the local power than there are available channels. The likelyhood of interference, or of deliberate eaves-dropping, is very high. I would recommend against using RF unless it is truly necessary, and then I would recommend caution in what you transmit! Dave Levenson Internet: dave@westmark.com Westmark, Inc. UUCP: {uunet | rutgers | att}!westmark!dave Warren, NJ, USA AT&T Mail: !westmark!dave Voice: 908 647 0900 Fax: 908 647 6857