Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request From: Julian Macassey Newsgroups: comp.dcom.telecom Subject: Re: FCC REN Numbers Message-ID: <8285@accuvax.nwu.edu> Date: 26 May 90 01:41:14 GMT Sender: news@accuvax.nwu.edu Organization: The Hole in the Wall Hollywood California U.S.A. Lines: 91 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 386, Message 2 of 7 In article <8185@accuvax.nwu.edu>, 0004261818@mcimail.com (David Tamkin) writes: > In volume 10, issue 377, Julian Macassey answered some of Steve > Friedl's questions about FCC ringer equivalence numbers. > I have three far simpler ones (I guess): > 1. What does the B or A after an REN mean? I think I covered this in an earlier posting, but then I could have glossed over it. The letter at the end of the REN numbers covers the "Ringing type" from the notorious Table I. A Ringing type A ringer is sensitive to 20 Hz +-3 and 30 Hz +-3. A B type ringer is sensitive to AC voltage between 15.3 and 68.0 Hz. Just for the curious, a C type ringer is sensitive between 15.3 and 17.4 Hz. There are many classes of ringers. I know that the class is supposed to refer to the frequency coverage, but owing to obscurity in the FCC regs, some labs measure type B ringers (Electronic warble type) as a type A so they can get a lower REN. This does not make it a type A ringer. This makes it a type B ringer measured as a type B. Apart from type B, other ringers cover a narrow frequency range. This frequency selectivity is sometimes used with party lines. It is also one of the factors that limits bell tap in US phones. See an earlier posting of mine where I waffle about this. Yes, most Type B ringers will also respond to frequencies above 68 Hz, like 100 Hz. > 2. If the ringer on a telephone can be turned off, does it no longer > count in figuring the total REN load on a line? I wish this was true. If you look carefully, you will notice that only the output transducer (fancy name for gong, Loudspeaker or piezo disc) is disconnected, but that the power consuming stuff is still on line. In a gong ringer the "off button" is often an arm that obstructs the striker, so no power is saved by turning it off. With electronic ringers, depending on the design, some power may be saved. I have quietly campaigned to have the off switch disconnect the ringer from the line. It does not disconnect the ringer because, it always used to be that way. But that was then when there was maybe only one instrument on the line. These days, you may want the ringer off, because you have too many on line. To take a ringer off line you have to actually disconnect it internally. In the old days, the gong ringer circuit was left in circuit at all times so the telco could sling an AC test circuit down the line at the dead of night and the ringer provided a return path. Note recent postings about strange telephone modems etc going chirp in the night. They also had records of your normal impedance, so any change could tell them if water was seeping into the line etc. It also told them that you had bootlegged a phone on the line. They then got snotty. Most techie types then learned to disconnect the ringer on any bootlegged phones. Now many residential lines have tons of ringers on them and they change continually - must drive the test board guys nuts - any comments from CO types? Most electronic ringers do not provide a good profile to telco test circuits, the exception I know about is the Motorola ringer IC. Motorola does it with a chain of Zeners. So one other point, the "low" or "medium" switch on most electronic ringers is in fact a resistor switched between the ringer IC and the transducer, so the volume is low, but the power consumption is often just as high. My ideal electronic ringer would have the low switch put the resistor on the line before the ringer IC and the off switch would remove the whole circuit from the line. Yes, I know that if the "low" resistor is before the IC, it will make the circuit touchy in the low mode, depending on available power it would either make no difference in volume or silence the bugger entirely. > 3. Two of my modems *do* have REN's, though neither has any sort of > bell or gong. They check in at "0.4 1.2B" and "0.5A 1.6B" > respectively. My other modem has a speaker and thus does make a noise > (but the speaker is powered by the electric utility, not the telco); > it has an FCC ID but no REN on it at all. If the REN is below a 0.1 REN, it can be listed as 0.0 or nothing at all put on the label. See above for dreary details on the funny A and B numbers. In truth, all modems I have seen are type B ringers. To prove this, feed say 60V at 60 Hz (yes power via a regular transformer) to a modem, betya it picks up if in answer mode. I wrote extensively about all this ringer stuff years ago in Popular Communications mag, but I suppose it wasn't all that popular then. Plus of course the editors used to bugger and censor my text so some of the more esoteric stuff was jumbled and meaningless by the time it reached the public and vulgar gaze. Julian Macassey, n6are julian@bongo.info.com ucla-an!denwa!bongo!julian N6ARE@K6IYK (Packet Radio) n6are.ampr.org [44.16.0.81] voice (213) 653-4495