larry@uunet.uu.net (Larry Lippman) (09/04/89)
In article <telecom-v09i0326m09@vector.dallas.tx.us> macy@fmsystm.UUCP (Macy Hallock) writes: > Rumor had it that more than one residence burned > to the ground due to shorted dial light transformers ! This is more than a rumor - it's true! Several years ago there was a "recall" notice about dial light transformers which appeared in major newspapers. The notice advised subscribers how to identify the transformer, and even had a full-size outline diagram to compare against the transformer. As far as I can recall, the offending transformer was NOT the familiar 2012A, but was a KS-spec equivalent which had a somewhat larger "footprint" - closer to the 85-type transformer in size. The 2012A and 2012B (18-volt version for speakerphones, repertory dialers and other accessories) were rather carefully engineered to undergo magnetic saturation upon short circuit, thereby limiting current to a safe level (not much more than 1 amp RMS), while limiting copper heat loss in the transformer to "safe" temperature levels. In addition, there is enough current-carrying capacity in station wiring (including the tinsel conductors of a station or handset cord) so that at least 1 ampere of current can be carried without any significant heating effect. So, the point is, I don't believe that the 2012A was the "offender'. Newer transformers become "cheaper", and therein lies the problem. As an example, the 2012D (an 18 volt transformer) is a real piece of crap; not only does it not have the protective potting of its 2012B predecessor, but even the AC power plug prongs are loose. <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> TEL 716/688-1231 | 716/773-1700 {hplabs|utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 | 716/773-2488 "Have you hugged your cat today?"