Ericsson AGF telephone exchange 500 line selector demo
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- เผยแพร่เมื่อ 28 ก.ย. 2024
- The Ericsson AGF telephone exchange was used all over the world for more than 50 years. The key element of these exchanges is a 500 line selector. This is a demo of the operation of such a selector. The missing parts are simulated with an Arduino microcontroller.
Thanks for this video! I'm an elderly {74} Canadian man who is more-or-less retired from designing & manufacturing {in my tiny home basement office & workshop} specialty electronic equipment for the geophysics community. I was entirely unaware of the Ericsson selector until this video. A very clever design, and quite possibly superior to {more compact than} the earlier Strowger step-by-step mechanism widely used in North America beginning in the late 1890s. The lesson we learn is that there are inventive people all over the world. God bless all of them - we stand on the shoulders of giants, to quote Sir Isaac Newton.
I like the description. Amazing it was originally built without electronics. I recently did a project that rings another rotary phone; the Arduino counts the dial pulses, switches 12 volts from powering the line to powering the ring generator, and sets the correct line selector relay to ring the other phone. Between rings, the Arduino checks for off hook voltage, if so stops the ringing.
Beautiful ! Knap werk en mooie demo van deze pannekoek 👍
Thank you for this video, I was originally a Strowger BT Technical Officer in South Yorkshire UK. left BT as an Ericsson AXE10 engineer and became a consultant (1998) at Ericsson Stockholm Network Operations Centre. I came across the bank system as part of demonstration at the Museum of Engineering in Stockholm whilst working and living there. Fascinating how both Strowger and this system had group and final selectors but used differing mechanisms as you have indicated the design of these systems was admirable. 🙂
How did the system work before the invention of an Arduino?
How was the number dialled remembered before being sent to the selector?
Mark, The dialled number was stored in a number of uniselector-type mechanisms. These uniselectors were then stepped back to their home position whilst at the same time stepping the 500-point selector. This process required a fair number of relays. The register was only required during the setting up of a call and could be shared by a large number of selectors.
Detailed description can be found in the Ericsson Review journal and Telephony II by J. Atkinson.
@@wimderkinderen1952 Many Thanks - Do you know I haven't seen my copies of Telephony for about 45 years, they are probably in the wardrobe upstairs so far back they are in Narnia.
This mechanism strikes me as being very high precision and therefore may be a little temperamental unless cared for by a highly qualified professional engineer, so not ideal for your normal Butt-Phone wielding GPO gorilla.
Well done! A clear explanation of how the Ericsson pancake switch works. Using the Arduino with relay drivers is a great way to do the demo. Thanks for doing this.
I remember seeing huge piles of these 500 systems lying in huge piles at scrap companies for recycling in the 90s in Sweden.
They were probably replaced by the EXE system.
The best thing was this system worked even if you had a local black out, you could use your phone.
Wow...These look a _lot_ more compact and space-efficient compared to more common Strowger (SxS) equipment! My country (At the time) used named (Latterly three digit) exchange codes and 4-5 digit subscriber numbers, and our exchange buildings are _huge_ in some places. Just imagine how much space would've been saved had the UK had used the „Pancake“ selectors instead! ☎😁
Dank U! 👍
@@dieseldragon6756 It is interesting to see how telephone exchanges evolved in different countries. The GPO in the UK chose Strowger in the early 1920s, when other systems were considered less mature. They also hang on to it much longer than other countries, probably for two reasons: a. they expected electronic exchanges to become available in the late 1950s, and b. thousands of technicians were trained to maintain Strowger and it would take time and money to switch to something else.
I see that it can only use one phone at a time, how was this deployed to allow for more then one phone call at once? If we had the maximum 500 phones you would have 500 switches and each phone would need to be connected via 500 wires in a horrific mess of cables, which I don't think is practical
See my reply to Gabor M. An exchange would have one or more stacks of selectors. They would cater for simultaneous calls of 10-15% of the total number of subscribers. Each selector in a stack has access to 500 lines, where each line only requires two wires to the outside world. The wiring is far less than with other exchanges such as Strowger (step-by-step).
@8:40 - This is why it used to be possible to dial an old telephone without using the dial (like when some overzealous soul put a padlock on the dial wheel). You just tapped the hook as many times as the number (tap three times, pause, tap seven times, pause, tap once then wait for the call to connect).
In telephone boxes in the UK you could make free calls by using the tapping trick, because the penny collection mechanism would disconnect the dial from the line, not the hook switch!
Ah, a fond memory. When a dial phone had a dial lock, I could (for fun) tap the hook as you described but only 10 times. This dials the Operator and I would say that my dial has problems would she please complete the call based on the numbers I would give her. Never got a no. Another way to get the same result that you described.
I remember as a young engineer working with AGF in Stavanger Telephone Exchange. I saw it later in a technical museum in Stockholm.
Thanks for a really good description and demo of the 500 selector.
Amazing, thanks for the demo, its a work of art :)
Does each user have their own selector?
During a call, each user has an allocated final selector, or - in a large exchange - a group selector plus final selector. However, an exchange only handles a maximum of 10-15% of all possible connections at any one time. When a user picks up its handset, its dedicated circuitry in the exchange searches for a free selector, and a register to translate the dialled number into the rotation and translation steps of the selector. All registers can be occupied when it is busy. The register is released once the connection is established but the selector remains allocated during the call.
Love this! Hope more people see it :-)
Thanks. Send the link to your friends 😁
Hi, thank you for this video, I have an old GSM 900 car cell phone (1993). In my country, 2G is no longer available, so the phone does not work anymore. I tried to find out if it would be possible to convert this phone to 4G, unfortunately I couldn't find anyone who could help me. What do you think, is such a conversion possible?
that is absolutely possible, but it would likely be difficult if you have never done something like that before
@@IANSYT Okay, and how would it be possible?
There are open source devices (and diy) that can generate old 2G signals, they still sell them to smaller countries and places that need to use older devices, you just need to do a little searching
That's fascinating, thank you. I've never heard of those devices before. Very nice demo.