What causes “ghost rings” on the telephone?

Dear Cecil: In my bedroom I have one of those cheap little extension phones — you know, the kind you get free with three rooms of carpeting for $299.95. Instead of ringing, it makes a little electronic warble. It also makes a tenth of a warble when someone picks up the phone in another room. Now here’s the thing: sometimes this tenth-of-a-warble occurs spontaneously. What’s more, it seems to happen at the same time every day — about 2 AM, when my wife and I are in bed. What’s going on? Is someone sneaking into our house every morning to make surreptitious calls? Is someone tapping the line — someone who knocks off for coffee every night at 2? Is Ma Bell, or one of her numerous offspring, checking up on us? Mike L., Chicago

Cecil replies:

Evidently the last, Mike, but having spent 18 months on this godforsaken topic (honest), I’m so punchy I hesitate to say for sure. The problem was never really finding out the answer. Cecil knew, in the calm and instinctive way he knows everything, that the cause of the mystery rings was some kind of automatic line-testing program run by the phone company. The trouble was getting the phone folks to admit it. Bell spokespeople conceded they did “trunk testing” of the lines that connected their switching centers, and opportunistic testing of customer lines whenever a call was put through. But they repeatedly denied there was any scheduled testing of individual phones.

I didn’t believe this, but before proceeding I thought it wise to get a little independent corroboration of the phenomenon, having gotten reamed on some of these techie conspiracy reports in the past. (One recalls with a shudder last year’s secret-message-in-Moonlighting fiasco.) When my minions appeared on radio talk shows, I had them ask if anyone else had experienced “ghost rings.” The phone lines invariably lit up, and it wasn’t ghosts on the other end. Callers said the ghost rings generally came at a fixed time, usually in the evening or early morning. Commonly there was a half ring or a full ring, occasionally a couple rings. But nobody was ever on the line.

Listeners of Eddie Schwartz’s late-night gabfest on (then) WGN radio in Chicago seemed particularly interested in the topic and devoted untold hours to talking about it. Speculation on the cause always got progressively woollier as the night wore on. Many callers blamed computer hackers, who allegedly programmed their modems to dial up phone numbers in sequence looking for data banks to plunder, a la the movie War Games. This theory had a certain paranoid charm, but why dial the same numbers night after night?

Others guessed it was telemarketing companies: sell-by-phone outfits supposedly had their computers dial up numbers to see if any were out of service. (Nobody could explain the purpose of this.) A few lunatics said that 2 AM (or whenever) was when the wiretappers changed the batteries on their equipment.

Meanwhile, I talked with people at Ameritech, AT&T, Bell Labs, and the like. Nobody would come clean. Figuring it was time for direct action, we returned to the airwaves and rounded up two volunteers: Penny, who got chirps on her phone between 10:38 and 10:44 every evening, and Pat, an answering-service operator who logged dozens of ghost rings a night on her multiline switchboard. I reported their cases to the phone company and said, OK, guys, here’s the facts. You figure it out.

A couple weeks later a Bell spokesperson called back. Son of a gun, he said, it seems there is a routine customer line-testing program after all. During off-peak hours a central-office computer goes around injecting a small voltage into each line to check transmission quality. The juice is too low to trigger a ring in most phones, but apparently a few are hypersensitive. The whole thing seems to have started when the phone company began replacing its old electromechanical switching equipment with new electronic stuff. Line testing on the old system never caused problems, but obviously the new system has a couple bugs. When the phone company suspended testing, the ghost rings stopped. When it started up again, the rings returned. Case closed at last. This job can be a pain in the keester sometimes, but it has its satisfactions.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.