A surprising coincidence - Page 1
Forum section: electronics / projects

author: icon
author_rank: Regular Contributor
timestamp: June 25, 2012, 04:13:41 pm
content: But then they all are, I suppose.I was given a old type 706 rotary dial phone  some years ago, and despite fooling around with the internal strap options, I never could get it to ring. Under the bench it went. I came across it the other day, and thought "fix it or chuck it". Armed with a circuit diagram, I found that one of the two ringer coils was open (should be 500 Ohms). A closer inspection showed a visible break in the wire just where it emerges from under the tape.(I'm going to get to the point of the story in a moment; bear with me.)I had to unsolder the thing to try and fix it - managed to unwrap a coil of wire and resolder it. Bingo! DDrrriiinnngg...DDrrriiinnngg. Lovely. Surprisingly, English exchange equipment, right to the present day, works with pulse dialling as well as tones. So now I have a spare phone that doesn't need power for a base station. The only downside is that 'downstream' equipment - like the BT messaging service - *doesn't* like pulses, so there are limitations.(We're nearly at the point now.)So I looked at XKCD for the first time in ages, and found that last weeks cartoon was this:http://www.xkcd.com/1072/Well, it amused me.RegardsJohn Like this (photo pinched because I didn't take one)

author: Dawn
author_rank: Regular Contributor
timestamp: June 26, 2012, 01:09:13 am
content: Tone access was a luxury in some parts of the states well into the 80's. Many home lines didn't support DTMF unless you paid an extra fee, so even wiring in a DTMF phone would do nothing more then open the loop and sieze a dialtone. Deregulation and technology forced that hand. While your phones were limited to pulse dialing, more and more calls to company's E/PABX systems were met with DTMF options for reaching someone or you had the option sometimes of holding for a lone, swamped operator. Private, long distance carriers required DTMF. One of the neat enhancements to a home, company set was a replacement mouthpiece on the handset that simply screwed in place of the old. It contained a circular DTMF pad & microphone operated from the carbon mic bias voltage. I'm sure those must have been available on your side of the pond. You could also buy a sloping,external keypads that would add DTMF functions powered from the loop voltage here. I'm sure it would have been just as economic to pay the extra amount for a DTMF subscriber set and DTMF activation until complete deregulation allowed for subscribers owning and purchasing phone sets retail.

author: Psi
author_rank: Super Contributor
timestamp: June 26, 2012, 01:32:18 am
content: Some types of those old rotary phones are extremely rear and worth a lot to collectors.Check if it's worth anything before you get rid of it.

author: arclight
author_rank: Contributor
timestamp: June 26, 2012, 09:22:45 am
content: Nice! I fixed one of the gas solenoids in my hot tub this way - the safety pilot worked fine, but the gas wouldn't come on. For some reason, solenoids almost always fail in the first couple of wire turns. I suppose that's where all of the stress gets concentrated from the termination, and it's not well restrained?ArclightQuote from: icon on June 25, 2012, 04:13:41 pm

author: Rerouter
author_rank: Super Contributor
timestamp: June 26, 2012, 09:45:02 am
content: also see the exact same on bimetallic gauges, its because the ends flex more when the coil heats or cools, and the fact that the last cm is generally free floating, and thus fairly fragile, sadly when most of these things where designed flexible high temperature adhesives wherent all that common,