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Views : 763,821
Genre: Education
Apr 12, 2024 ^^
warning: returnyoutubedislikes may not be accurate, this is just an estiment ehe :3
Rating : 4.92 (703/34,543 LTDR)
98.01% of the users lieked the video!!
1.99% of the users dislieked the video!!
User score: 97.02- Overwhelmingly Positive
RYD date created : 2024-08-21T07:47:26.634167Z
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Top Comments of this video!! :3
Ah, this is such fun to come across! Reminds me of some fun times back in the mid 1970sā¦ I used a version of this idea as a teen to create a 24/7 ready live phone connection from my basement bedroom in my house to my best friendās house using just two Bell System Western Electric telephone handsets, a couple hundred feet of speaker wire and a 9-volt dry cell battery. I dug a slit into my lawn to hide the wire run around from the back of my house to the storm drain manhole cover near the street, then down and under and across the street, all around the back and up to my friendās 2nd floor bedroom.
I was overwhelmed to realize I could hear pretty much every conversation in the house so I needed to add privacy switches. Eventually.
Some 20 odd years later a lawn worker had my dad come out to try to figure out what heād just dug up. š
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Many years ago ( around 1977 I think ) a buddy and I had a setup like that, but there was about 1500 feet of wire between the phones, and yet, we used 9V battery to be able to talk. We didn't have the voltage available to get a ringer, so we had a headphone plug on each end, and played music from our walkmans to get each other's attention. Wire was run through the trees and along the fence. When there was a short from wet grass hitting the electric fence wire, the phones had the lovely BUZZ.... BUZZ... BUZZ... on them.
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As an old school phone engineer I can tell you most people leaving comments are correct about the tip/ring voltage being 90V but the little known part is that its at 20 Hz as phone system predates national electric grid that went with 120/240V at 60Hz... That's why a hot phone wire grabs you so much harder than 120 electric... The lower frequency Hz contracts muscles and higher frequency Hz releases muscle...
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Old Linesman here from South Africa: If I remember correctly we had about 90V or so at 17 Hz for the ring and the normal ~50Vdc from the exchange battery when the handset is lifted. You are correct. There is an isolation microswitch inside the phone that disconnects the "phone' part when it is on-hook, so that no current is drawn when the phone is not in use.
Great Video!
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I remember back around 1985 or so, I knew a couple electricians that used old public phone hand sets and connected a 9 volt battery inside it, wired it similar to what you did, add alligator clips on the wire and would use it to trace wires in conduit. By that I mean they would have a large conduit with dozens of different power wires in it and they all looked the same. One guy would clip one lead to the metal conduit and then the other clip to one wire. The next guy would clip one wire to the conduit and then touch one wire after the next until they 2 guys could talk to each other. Then they would put some identifier on that cable and continue to process until all the wires were traced.
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From what I know from techs and measuring in the past in Australia. I used to measure ~52volts as the batteries would be floating around 54.4 volts dc(some diode drops). After the old relay system was changed to to MOSFET switching it went to 48 volt DC. Now on hook was ~48 volts give or take it's not critical, over 9 would generally work. Off hook the phone would pull the line down to around ~ 12 volts depending on the phone. And ringing was 70 volts ac supper imposed on top of the ~ 48 volts DC. After a blocking capacitor to block the DC part the 70 volts ac 25Hz would make a relay hit a bell either side like an old alarm clock did. DC current was limited to 30 milliamps (0.03 amps) but later I measured 40 milliamps on the MOSFET digital system. Ring current was limited through I think 2K4 (2,400ohm) resistor) Giving about 2 watts (70 / 2400 = almost 30 milliamps) of ring power. Line impedance is 600 Ohms for the audio.
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I wish I still had a 20 page Rafio Shack book from my Phreaking days, which listed the minimum amd maximum tolerances for the system as set up by Bell Systems, reviewed the pulse and DTFM dialing systems, the switching gear in the central office that complete the selection operation, a basic overview of operator and automatic pay phones and a basic overview of long distance switching, selection and dialing functions.
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@efranklin85
4 months ago
Former AT&T lineman here šš¼. Ringing voltage can vary, but what is produced at the source in the central offices out to the lines is 105 volts ac. It can drop some at the home depending on the condition of the lines. Talking voltage was 48V DC. The COs have giant banks of 48V batteries and diesel generators for backup in case the power goes out so people can still call out in case of emergency. Also, when itās raining and working on the lines you can get a Hell of a shock that vibrates your whole arm if you hands are wet. Forget about it if someone calls in on the line youāre working on. It wonāt kill, but itāll make you think twice before grabbing that line again. š
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