EMF2024: Strowger Installed and (mostly) working
Well, that was a wild ride! I'm writing this after the event, I'm still trying to process what went well and what didn't go so well... but here's the story.
Wednesday
I packed up the last of the exchange bits into crates, worried a bit about what I'd inevitably forgotten to pack, and then CuTEL turned up with their van. We had hoped to be able to reverse it onto my driveway to make loading the exchange into the van easier, but the lane and the vans turning circle were both too narrow to allow that.
Between myself, the 2 CuTEL volunteers, and my next door neighbour we got the exchange wrestled into the van and headed to site.
The site had been sujected to a lot of rain a couple of days before and the ground was far too soft for us to get the van as close to the container we were installing the exchange in, so we parked up at the end of the trackway and decided it would just need some brute force.
We grabbed some volunteers, and between 6 of us we picked up the exchange and carried it through Null Sector, and installed it in the container furthest from the entrance.
I set about unpacking, and trying to get the exchange up and running. I hit several problems, including a connection to the EMF network that just wouldn't play ball...
I got some phones out on the table and working though, so I knew at least local calls would be possible
Thursday
Thursday was "arrivals day" do Null Sector wasn't open to the public. I spent most of my day working on the exchange, chasing down problems, and trying to get the network connection working. I eventually traced it to a patch lead that wasn't making good connection.
An easy fix surely? Well, the patch lead was part of a run that went across the top of 4 containers, from the DJ booth down to where the exchange was. I spent an hour or so running around on top of Null Sector removing the problem cable and running a replacement (that didn't have a joint half way down it!)
I had internet! Result!
I couldn't place any SIP calls though, it was weird, it was like my calls were being rejected by the EMF phone network core. I reaced out to the POC for help, but they were super busy getting the main voice network up... which was reasonable!
Friday
I took another swing at the SIP problems in the morning, and worked out what was going on! At some point in the network troubleshooting I'd commented out all the SIP registrations in the asterisk config to reduce the log noise. Doh!
I re-enabled them, and the connection to the phone core came up. I could call from my exchange to the DECT phones, and from the DECT to the strowger!
I shut the exchange down and went for some lunch, and to see some talks
7pm, Null Sector opened. I opened up the exchange and omg was it popular! The crowd was 5 layers deep as people clustered around it to see it working, play with the phones, and try their hand at dialling into/out of it from their phones.
I spent 5 hours that evening talking excitedly with all sorts of people - that's what I came for!
The exchange is 70 years old though, and that evening it worked harder than it has done since it was in service... anything that was a marginal adjustment at the beginning of the evening was a fault by the end.
Saturday
I went over to Null Sector about 9am to try and shake out some of the faults. It wasn't long before people started to show up and express interest. A much calmer (sober!) crowd filtered through the doors all morning, and I had loads more enthusiastic conversations. I didn't get much fixed, so I busied out the most faulty selectors.
We were down from 5 working to just 2 working final selectors.
Further testing of those remaining selectors revealed they both had faults with their tie lines. Some relays weren't operating decisively enough, and the resulting contact ounce was occasionally inserting extra pulses.
This meant if you tried to dial out to extension 1234, sometimes you'd an extra 1 inserted (eg 11234) or sometimes one of the digits would increment (eg 1334) - this fault wasnt' predictable, didn't always happen, so I couldn't correct for it in software.
I spent some time between conversations trying to pin it down, but I got nowhere. Instead I altered the signage, and started telling people they could dial in, but not dial out.
I closed down for a few hours in the afternoon (to go eat and see talks) and came back early evening, for another long session of talking to people.
I only closed up because there was a DJ I wanted to see...
Sunday
I was tired, and so was the exchange. One of the selectors that had been limping along the night before was now faulty. I had another try at reviving it, and while I did so it became clear that I'd have to try and run on a single selector.
Trials with the first group that turned up quickly showed that it wasn't going to work, as people don't really understand when you try to explain that the massive piece of equipment behind you can only handle one simultaneous call... so I started to pack the phones away until there was only 2 demo phones on the table.
By now word had got around that you could call in to the strowger from around the site though, and people were trying to do that while people were trying to use the demo phones. This wasn't going to work!
I had a fallback plan though.
I removed all the demo phones and switched off the exchange. I pulled a selector out of the rack and instead focused on showing people how the mechanisms work. This again was very popular, and I was in Null Sector talking about telephony until midnight!
Monday
Today it was time to pack it up and take it home. I spent a couple of hours in the morning packing it all away into boxes, then around 1pm we wrestled it back into the van and took it home.
There are faults on every selector, I have suspicions about some of the tie line circuits... but nothing is so broken that it can't be fixed.
I'll give the exchange a bit of a rest for a few months, then start chipping away at it one fault at a time.
The PAX will live again!
Lessons Learned
Taking a 70 year old phone exchange to EMF was a silly idea, but I have no regrets! I did learn a few things though:
- Hiring moving crates is a game changer. So much easier than assorted boxes, and cheap too! I paid £1/box/week - a bargain.
- A sack truck with big soft tyres would have made moving things a lot easier
- I completely suck at planning logistics
- If you have things in three places (exchange, motorhome, car) you will never be in the same place as the thing you need
- Next EMF, take something that doesn't need constant care and feeding! I'd have loved to see more of the event, or volunteered, or met more people... but I was so busy having amazing conversations about phone exchanges!