Ian, Chris and I went to the NVCF last weekend. It’s a bit like a combination of a specialist antiques fair, a car boot sale, and the contents of your grandads garage.
As well as all the old radios, televisions and telephones, there was a selection of test gear with amusing manufacturer names. Pfft! Wayne Kerr!
I was called over to one stall to try and identify this piece of equipment. It was apparently recovered from a BBC building somewhere, and it’s an optical disk player. The disk has sound encoded on it as a black line of varying width. There’s a lamp on one side and a photoresistor on the other. When the disk spins, the amount of light falling on the photoresistor changes the current passing through it, giving you audio. It’s only got one disk, although it appeared to have several (5?) messages recorded on it. The photo detector didn’t appear to move though, so I think changing messages was probably a manual operation. These machines were often used to play back messages like “all lines to London are currently engaged” or similar messages.
I didn’t get any closer to identifying it, and whilst I was intrigued by the message it might contain – I wasn’t intrigued enough to find space in the car for it. Besides, Chris had filled most of the car with radios by that point!
I managed to spend about a tenner and got various bits and bobs including this clock unit. The displays are interesting. They’re a stack of plastic laminates, each one has a numeral engraved on it. Each laminate has a lightbulb which illuminates it from the edge, causing the numeral to glow. It’s quite clever, and undoubtedly pretty. It’s a bit tricky to drive with modern technology (and where’s the fun in silicon anyway?!) so I’m going to build a clock out of uniselectors to drive it instead.
I think I can get away with 1 uniselector for the hours (using 24 outlets of a 25 outlet uniselector, with two banks driving both digits and a third bank which can be used to skip the last position) and two uniselectors for the minutes (one per digit, each with 2 banks. One to drive the display and the other to skip unused positions) – the circuitry to step the uniselectors once a minute should be fairly straight forward.
It would be easiest if I can generate a 1 minute pulse from somewhere, but I’ll probably drive it with a 30 second pulse so it’ll be compatible with a GPO master clock if I ever get one!
Along with the associated relays, that should all fit nicely in a box underneath the display.
It was the THG Swapmeet at Avoncroft museum of historical buildings today. I didn’t take much with me to get rid of this time (partly because I’ve got rid of a lot of stuff already, and partly because I was too lazy to organise getting rid of anything) but I came back with a pile of books, some posters, a Buzby tea tray, a box full of useful krone spares for the railway (including some test leads which should make verifying anything we do much easier) and most of an AT&E Type 6 phone.
I’ll write up more about the phone some other time, but I’m dead excited about it – because it’s the phone which would have been supplied with my small PAX (and probably my larger one as well, but I can’t find any documentation to confirm that) - I’ve been looking for one for almost 3 years now and have at last managed to find a base, dial, and handset. I’m missing the case, but I can probably modify a 706 case to fit, which will do until I can get the “right” case) If anyone has one lying around they’re willing to part with, I’d love it!
Yeah, I thought not.
Also happening at Avoncroft today was some kind of civil war re-enactment. The avoncroft website says:
Experience British troops of the 1770s drilling and making ready to take control of the rebellious American colonists. The Lexington Militia will try to prevent the redcoats from searching their homes and town. Will King George’s army be able to keep control?
But I could have sworn the lady said it was described as “the last English civil war” – although, I suppose the begining of the war of independance could be thought of as an English civil war. Still, they looked jolly dangerous with their guns and whatnot, even when they were just chilling out with their ladyfolk!
I had a bit of a poke around Avoncroft as well while I was there. They’ve got a lot of buildings, and I’ve seen some of them before – but have never explored properly. They’ve got some dead good stuff! My favourite was probably the ice storage house because it was dark and echoey – unfortunately it doesn’t photograph very well, because it’s just a circular brick chamber with a lot of insulation. The windmill made up for that though…
Their prefab house was amazing (I really wanted some old guy in a cardigan to sit in the chair for me to take photos of, but there wasn’t anyone suitable around, and you could only view the rooms from the doorway anyway) but their prefabricated church was just as ace, and much easier to photograph!
While I had my camera out, I also took the time to sit down for 10 minutes, have a good think about my surroundings, plan a photo, and then shoot something for this weeks photo-challenge. It was this gnome. I rather like him, and am quite please with the wonky breaks-most-of-the-rules composition.
A long time ago, in a newsgroup far away (rec.juggling) I declared that I was going to build a telephone which would validate siteswaps for you. It was a hardware project for which I built the hardware, then got bored before I tied up all the loose ends on the software side of things, lost a load of code in a hard disk crash… tedious. It got pushed to one side. Until now!
Siteswap is a mathematical notation system for juggling patterns, where a string of numbers represents a sequence of throws. Each number determines how many beats later the object thrown, is to be thrown again. There’s more mathsy detail than you ever wanted on the wikipedia page: http://en.wikipedia.org/wiki/Siteswap or you can watch this youtube video for a reasonably clear explanation:
Suffice it to say, not all strings of numbers are valid juggling patterns. Some strings of numbers, if you were to try to juggle them, would result in two balls langing at the same time in one hand, or a ball needing to be thrown from a hand which is empty because no balls arrived there in time to be thrown.
So you need some way to check a string of numbers to see if it’s a valid siteswap or not. There are various ways to do this by hand, and various people have written software to do it for you. Every so often, geeks get hold of the idea and do things like “write the shortest possible siteswap validator in perl” I think the record for that is currently 28 characters:
1/grep$a[($_+$i++)%$.]++,<>
Recently Vakor posted that he’d built a regex which validates a siteswap. This has been attempted in the past, but previous versions used a chain of several regular expressions and required the siteswap to be repeated in the input. So I was impressed that he’d managed to do it in one shot – even if the regex is “unweildy” to say the least!
Anyway, all of this combined with me sinking my teeth into asterisk recently made me think I should have a crack at writing an asterisk macro which can validate siteswaps. So that’s what I’ve done! If you’re interested in the code/samples you can download it from http://paulseward.com/downloads/siteswaphone-1.0.tgz and if you want to play with it – you can call it on 0117 9115202 (or +441179115202 if you’re outside the uk and feel like paying for an international call)
If you’re not a juggler and just want to hear what it does, 97531 is a valid siteswap, but 97532 isn’t.
There’s no real phone on the end of it or anything, so feel free to call it day or night. It can only handle one call at a time (because I’m too cheap to pay for multiple incoming lines for a toy like this!) so if you get busy tone, just try again later.
Yesterdays update was about BOV, so it’s only fitting that todays update is about the other large project at home, my phone exchange.
Since my last update back in September, I’ve made a fair bit of progress and uncovered one incredibly perplexing fault.
Progress first…
I built a frame to hold a single U-Point (very kindly provided by Martin Loach, thanks Martin!) so I could mount my outgoing junction selector. This has been cabled up and is accessible from outlet 30.
The electronic PAX I had wired in to the outgoing junction selector went “pop” so now the only thing hanging off it is a route back in to the 50/7A
I added a sipgate trunk to my Asterisk box, so I now have a landline number which causes my exchange to rattle into life.
The outgoing junction selector wasn’t homing smoothly, so I readjusted the interrupters and it’s much happier now.
Somewhere in there (but not documented in my local exchange diary, because it was work done at the railway) I also got my PAX talking to the UAX at the railway again.
Perplexing Fault:
FS3 has a fault. The outgoing tie line to my asterisk (50) works fine, but if I try and go out the junction selector (30) FS3 just skips over the bank position, lands on outlet 11 and returns busy tone to the caller. None of the other 3 final selectors I’ve got have the same problem, and if I swap selectors around the fault follows FS3 (so I know it’s something in the selector rather than the shelf position, the multiple, the line circuit for 30, the outgoing junciton set or anything like that)
Closer inspection when it’s misbehaving reveals that the H relay doesn’t pull in when the selector lands on 30 (but it does when it lands on 50). Manually operating the H relay causes normal operation, and I can dial through the tie line without any problems – so something in the path for the 900R winding of the H relay isn’t happy.
My first thought was that perhaps the wipers were out of alignment and that somehow I was getting an earth on the PN wiper (which would happen if 30 was busy, and skipping on to outlet 11 would be desirable behaviour in that case). Not an unreasonable theory given that I had to set up the wipers on FS3 back in August 2012 – and when setting up wipers I generally use level 5 as my reference level (and we’ve established that the tie line on level 5 works)
However, if I busy out the selector, including the vertical/rotary magnets, and manually position the selector on outlet 30 – all the wipers have the conditions I would expect on them. Indeed comparing them with another selector in the same state revealed no obvious differences.
As usual when fault finding, I gave all the relay contacts etc a good clean, and checked they were making/breaking contact (that didn’t make any difference either)
Consulting the diagram notes has shown that it’s something in the path from (NEG, 1300K, PN bank and wiper, 900H, C7, 500G, TL5, E2, NR4, N2, B1, POS) but it’s getting a bit late at night to be poking about in that sort of detail – so it’ll have to wait for another day.
Before THG swapmeets, Sam Hallas produces a list of things he’s getting rid of – either for free or for a charitable donation. I’ve decided this is a marvelous idea, so I’m pinching it and giving away a box full of junk ”interesting telecommunications artefacts” at the Milton Keynes swapmeet.
If you want to give me a donation, I’ll punt it on to macmillan cancer support in recognition of the help they recently provided to a friend of mine and his family in his last few months of his battle with oesophageal cancer. I intend to match the amount raised, so feel free to stitch me up with a large donation ;)
Tele 280
I’ve got two of these I don’t need. They could both do with a bit of TLC, although the dials move freely so there shouldn’t be too much wrong with them. One has no plug at all, and the other has some croc clips. (Martin Loach “at least one”)
Amplifier and Loudspeaker No 5
This seemed like a good idea when I picked it up, but I’ve never found a use for it. Not tested, but they’re not particularly complex beasts. It’s quite tidy with no major cracks or scratches and the line cord is in good condition. (David Williams)
50V, 15W soldering iron
This one is in a bit of a sorry state! It needs a new bit and the cable has been melted several times. Not tested for obvious reasons. (Kevin Dodman)
50V Desoldering Pump
This is untested as well, although the rubber bulb is a little tatty (not surprising given its age) but it appears to be intact and there is at least a little suction. (Martin Loach)
50V Headlamps
One of these is filthy but with a complete cable, the other is clean but without a cable. Neither has bulbs. (David Williams)
Faceplate
This faceplate mounts a 700 series line cord in a standard patress box. It’s marked “GPO” but I have no more information than that. (Ian Stubbs)
Viscount Phone (Grey)
Pulse Dialing, Grey, “Viscount” phone. Believed to be working.
Statesman Phone (Grey)
Pulse Dialing, Grey, “Statesman” phone. Believed to be working.
50A Ammeter
50A Ammeter. I don’t have anything which pulls that much current! (Martin Loach)
High Speed Relay contact covers
I picked these up thinking they were standard 3000 type relay contact covers. They’re not, they’re for high speed relays and I don’t have many of those in any of my kit. I’ve not counted them, but there are at least “several” in the box. (Martin Loach)
Goldstar Ring Generator
New, boxed, I bought this off ebay with the intention of using it for my homebrew phone exchange – then acquired a Ringer 2A the following week (which is clearly more awesome!) This one cost me almost £30 so has got to be worth a donation of some sort. (Howard Orgel)
Call Baring Unit
I can’t remember where this came from, but it’s new, boxed and I’ve got no use for it so it’s going! (Mike “Buzbybest”)
Megger
It’s a megger of some description. Not tested, and the meter glass is cracked (see photo) – I’ve seen these go for a fair bit recently on ebay but it’s too heavy for me to be bothered with posting so it’s yours for a donation.
My collection of phone exchanges hasn’t really grown at all in over a year now, but they’re still all very much isolated islands. You can’t phone from one exchange into any of the others (with the exception of the 50 line exchange and the asterisk server, which are connected by a tie line which you access by dialling 50) – I’d like to link them all up, in a manner similar to that shown above.
Extensions on the asterisk server are 2 digits (because it makes the dialplan consistent) To get from PAX extension 26 to VOIP extension 81, you dial 5081. The 50 connects you to asterisk, and 81 connects you to the VOIP phone. The asterisk server has been set up so that you also dial 50 to access the PAX, so from 81 you can dial 5026 to call in the other direction.
This gives a nice consistent 4 digit dialing scheme! Great!
My 10 line PAXs throw a bit of a spanner into that though as they have a single digit numbering scheme. I can have extra outgoing tie lines from the 50 line PAX (for example on 30) but if I were to connect them directly, they’d be 3 digits and that would *never* do!
So at the weekend, I designed and built this relay set. It hangs off the 30 tie line, and stores the next digit you dial. Depending on what digit you dial, it can connect you to one of up to ten 10 line exchanges (I don’t have 10, but it’s best to plan ahead!) So now, Dialing 30 connects you to this relay set, dialing 0 connects you to a 10 line PAX, and then you can ring the phone at extension 4 – giving you 3004! Yay! 4 digit phone numbers!
OK, so going the other way isn’t quite as neat (Dial 0 to get out of the 10 line PAX, then you’re landed straight into the 50 line, so dialling 026 will ring extension 26, or 05081 will dial VOIP 81) but it’s better than nothing… and my ATE 10 line PAX doesn’t have any outgoing tie lines at all yet so I’m not that worried!
Anyway, I’m quite pleased with this project as it’s the first non-trivial relay set I’ve designed, built, and debugged without assistance! I say designed, most of the circuit elements are pretty standard. The junction half of the circuit is based on the auto-auto junctions we use at the railway. It’s a pretty basic stone transmission bridge, with 2 stage dropback and the A2 contact repeating dial pulses out to the line.
The uniselector which reacts to the dialed digit is controlled by a circuit based loosely on the stepping circuit from a PABX4 group selector but with some modifications to work with a uniselector rather than the 2000 type selector used in the PABX4.
For example, uniselectors don’t have “off normal” contacts (mechanically operated contacts which close when the selector steps off its home position) so instead I’m using the homing arc on the uniselector I’m using for the same purpose. It’s also used to drive the uniselector home at the end of the call.
Oh, and thanks to the asterisk server at the railway having extension 491 configured to dial back through my exchange to ring extension 26, and me hooking outlet 9 on my new junction selector back in to the 50 line pax…
I can now call from extension 25 to 26 by dialling: 50309500491 – which goes through my 50 line PAX to the asterisk (50), back into my pax and back out again to my new junction set (30), back in to the PAX again (9) and then back in to the asterisk box (50) off to the railway (0) and then back through my asterisk server and back into the PAX to ring extension 26 (491) – *phew*
Gloriously pointless, but it yields surprisingly good call quality and not a single pulse was lost!
Back in 2000, a couple of THG members got together and produced the TIM2000 speaking clock. It’s been out of production for a number of years now, and when examples do come up for sale they’re expensive (reflecting both the rarity and the high cost of the original device!) It also uses the MSF radio time signal to set its clock, which isn’t so reliable in much of the UK now that the transmitter has moved to Cumbria.
Technology has moved on, and a few people are planning on having a go at making a TIM2012 (or more likely 2013!) equivalent version with a modern microcontroller at the heart of it. PICs and dev boards like the Arduino have made microcontrollers more accessible and easier to program. Modern storage has come down in price a lot, so where the original used an eeprom to hold the audio samples we can now make use of SD Cards etc – the gubbins for interfacing audio onto a telephone line is easy enough.
Because the storage is removable (and huge!) We’ve got the opportunity to do cool stuff like offer multiple voices, allow people to easily record their own voice etc! Lots of possibilities.
I’m a bit excited by the idea so I’m diving in to see if I can swim anywhere.
I’ve bought myself an Arduino Wave Shield to go with my Arduino and have a play with with as a prototyping tools to see how close to a proof of concept I can get. I spent about 40 minutes putting it together this evening and have yet to play with it.
Word on the street is that the libraries recommended for use with the Wave Shield (for handling playback and all that) are a bit heavyweight and might not fit in the ATmega 168 I’ve got, so I’m going to either have to cut down the library size somehow by getting rid of the bits I’m not intending to use, or suck it up and upgrade my ATmega168 to an ATmega328 – which will cost me all of £2.20 (not sure I can stretch to that!)
Anyway, if I can get any of this to work, I think it should be possible to prototype up a TIM2012 for about a third of the cost of the original production model, and if it goes as far as designing a PCB I think we can get the price down to about a third of that again.
My description of priority calling in yesterdays post wasn’t quite accurate. I’ve dug out the Operational Bulletin and checked. It says:
3.4 Priority Service
An official having this service may speak instantly to any extension on the exchange, whether the extension is already engaged on a call or not.
The caller dials the required number and the Link Selector wipers extend the call to the required line.
If this line is free the bell rings and the called extension answers. If the called line is engaged no Busy Tone is heard and the caller is instantly switched into the existing conversation.
The call at this stage is not private; when privacy is required both engaged parties must replace their handsets, ringing current is then automatically connected to the required party’s bell and the call proceeds in the normal manner.
The circuit diagram notes say this:
7. Priority Facility
The priority facility enables an extension to speak to an engaged extension when the line that is dialed is already engaged.
An extension line with priority has tags K and PC strapped on the tagblock. On completion of dialing the two digits, relay G operates if the line is engaged.
Relay G operated:
G5 completes a circuit to operate relay E (NEG. 800E, C2, G5, (TL6) (NPB) S1, T1 & 2, U3, FS bank tags PC to K, K2, L1, FS (P) bank, U27, B6, T9 and 10, POS)
Relay E operated:
E1 completes the circuit to operate relay D (NEG. 200D, 500YB, G3, NR1, E1, B1, POS)
E4 disconnects Busy Tone from the calling line.
Relay D operated:
D2 & D3 complete a speech circuit across the called extension lines and the caller can speak and hear.
If required the priority extension may request the extensions to clear the call in order that he may speak in secret to the required party. In this case on the line circuit of the required line being restored, NEG is replaced on the PN wire from 1300K, in the line circuit and relay H is now operated from (NEG, 1300K, PN bank, 900H, C7, E2, NR4, N2, B1, POS)
Relay H operated:
H6 releases relay G followed by relays D and E.
With relay E normal, ringing current is connected to the called line at E3, and the call proceeds in the normal manner.
So that’s how it’s supposed to operate. How does the modification I’ve got change this operation?
This diagram should ideally be read in conjunction with the original diagram – as the diagram above doesn’t show the whole circuit, just the PC modifications (with a few relevant bits of circuitry just so you can orientate yourself on the main diagram!) As far as I can tell, the new sequence of operations is:
Relay PC operates:
PC is operated as follows: (NEG. 2000E, (TL6) (NPB) S1, T1 & 2, U3, FS bank tags PC to K, K2, L1, FS (P) bank, U27, B6, T9 and 10, POS)
PC2 completes a circuit to operate relay E (NEG. 800E, C2, G5, PC2, (TL6) (NPB) S1, T1 & 2, U3, FS bank tags PC to K, K2, L1, FS (P) bank, U27, B6, T9 and 10, POS)
Relay G operated:
G5 completes a circuit to operate relay E
Relay E operated:
E1 completes the circuit to operate relay D (NEG. 200D, 500YB, G3, NR1, E1, B1, POS)
E4 disconnects Busy Tone from the calling line.
Relay D operated:
D2 & D3 complete a speech circuit across the called extension lines and the caller can speak and hear.
If required the priority extension may request the extensions to clear the call in order that he may speak in secret to the required party. In this case on the line circuit of the required line being restored, NEG is replaced on the PN wire from 1300K, in the line circuit and relay H is now operated from (NEG, 1300K, PN bank, 900H, C7, E2, NR4, N2, B1, POS)
Relay H operated:
H6 releases relay G followed by relays D and E.
With relay E normal, Int Ring Tone is connected via PC1 to the called line at E3, and the call proceeds in the normal manner.
I have no idea why you would do this.
Int Ring Tone isn’t designed to ring a bell (it’s a tone!) and as far as I can tell, the only conditions under which PC1 is operated are when the called party is off hook – so I’m at a complete loss as to what this mod was attempting to achieve. Having documented it thoroughly, and spent a number of hours headscratching trying to work out what it’s for… I think I’m going to declare it useless and reverse the modification.
It’s been over 6 months since I last updated on this project, which is a shame because I’ve done rather a lot since then!
Apologies if you’re one of my non-telephone readers, this probably isn’t going to be a very interesting post, and it’s rather long. I’ll make up for it by trying to go for a photowalk tomorrow or something.
February:
The biggest bits of progress in Feb were that I started fitting the TL (Tie Line) relays to the selectors, and built an asterisk VOIP server. The two projects are linked in that the TL relays are needed to allow me to call through my PAX and into my asterisk server. I did actually blog about the TL relays at the time, but I don’t appear to have mentioned asterisk here before.
While I did most of the modifications to my first selector in Feb, it didn’t work.
March:
March was a productive month. If you look at the selector which is 3rd from the left in the picture up top, you’ll see it’s got an extra relay. This appears to be a non-standard local modification from when my PAX was in use at the Ffestiniog Railway. I spent some time in March mapping out what it does.
It appears to be related to the Priority Calling feature these exchanges have. If I’ve read it correctly, it works something like this:
Alice is in conversation with Bob, but Mr Miggins (Bobs manager) wants to talk to him urgently. Mr Miggins has Priority Calling set up on his extension (because he’s a bigwig!) and dials Bobs number. Bob and Alice get interrupted by a bust of ring tone to signal that they should end their call immediately and hang up. When they hang up, Bobs phone rings and Mr Miggins can tell him off for flirting with Alice on company time.
In its original form, the circuitry connects Bob and Alice to ringing current (designed to ring a bell), but with this modification it connects them to ring tone instead (the sound you hear when a phone is ringing) I’m not entirely clear why this is useful, or why it needs a relay to achieve this!
Also this month, I bought a BT Voyager 220V adsl router from a car boot sale for £1. I reconfigured it to work as an ATA and give me a phone on the DFR telephone network. I did start writing up how to do that, but it turns out not to be all that easy to describe. I’ll come back to it at some point as ATAs usually cost around £30.
I cleared a load of faults on the selector I’d modified (FS2), learning a lot in the process
April:
FS2 developed a release fault, which means that at the end of the call, the selector didn’t restore to normal but instead got stuck. There are some clever widgets called “heat coils” which stop things from catching fire when this happens. Here’s a picture of them on the PAX:
and here’s a closeup of one of them:
They have a pin (on the right of the picture above) which is held in the body of the heatcoil with a drop of solder. The idea is that if the release magnet gets held on the current flowing through the heatcoil causes it to heat up, melting the solder and pulling the pin out. The mounting then springs apart, earthing a contact which in turn lights the alarm lamp so you’re alerted to the fault.
Heatcoils appear to be next to impossible to get hold of, so it’s a good job they can be repared by carefully pushing the pin back in with a hot soldering iron.
May: I didn’t get anything done to the PAX in May, probably because I was rushing around like a mad thing trying to do up BOV and then I switched everything off and went on holiday for 2 weeks.
Actually, I tell a lie. Looking at the svn commit messages, May was the month I got my asterisk server talking down a SIP trunk to the server at the railway. I can now call from my office at home, through my PAX, into my asterisk box, through the internet to the asterisk box at the railway, out into the UAX13, then out through a junction and a few miles up the road to a PABX4 and listen to the test number.
Which is nice.
June:
I came back from holiday, built a charging unit for the PAX batteries – then switched my asterisk server back on, only to discover that it wouldn’t boot.
I decided to leave phones alone for a bit and work on BOV instead.
July:
I traced the asterisk fault to a dead compactflash card, so I resorted to old fasioned spinning hard disk instead (so much for low power consumption!)
This was a pleasing experience, because 95% of the config for the server was in svn so it was dead easy to reinstall everything and get back up and running. I did identify a few things that weren’t in svn and documented them in the form of a shell script – and checked that in to svn. Sure it’s not quite puppet like I use at work… but it’s better than nothing.
I then turned my attention back to FS2 which was still causing problems.
My paper exchange diary shows lots of slow, careful, methodical troubleshooting (cleaning contacts, adjusting spring sets, that sort of thing) – eventually resulting in me realising that white heatcoils are no good, only green will do – and declaring FS2 successfully modified – a mere 5 months after I started. “must do better” I thought.
August:
I started adding the TL relay to FS3. Managed to get all the wiring done in one evening! It took me almost 6 hours, and by that time it was too late to be testing it incase the rattling/swearing woke up the neighbours.
Needless to say, it didn’t work first time – and had a really odd fault. Dialing 50 caused the line circuits for 63 to pull in and you end up back at dialtone – which allowed you to dial another number! That’s not right at all! I checked all the new wiring and it was fine.
*scratches head*
Purely by chance, during one test I noticed that one set of wipers was horribly misaligned and was shorting out all sorts of stuff it shouldn’t be! I realigned the wipers and it worked! Yay! I now had 3 working TL selectors!
High on my success, I tidied up the 50 pair tie cable on the back of the PAX, fitted a battery isolation switch, tidied up all the mains cabling for the asterisk/charging circuit etc then set about adding a tie line relay to FS4.
That went much better. Having learnt from all my previous mistakes, it only took about 4 hours to wire it all out and it worked perfectly first time.
2012/08/12 – a year and a day after bringing the PAX home from Ffestiniog it had 4 working TL selectors. I did do a bit of a happy dance in the front room, and the cat gave me a dissaproving look.
But wait! There’s more!
I added a speaking clock to my asterisk server, with the voice of Pat Simmons. Pat was the second voice of the GPO speaking clock in the UK from 1963-1985 (the first being Ethel Cain, from 1936-1963) – I’ve started to build something similar with Ethel’s voice, but suitable recordings don’t appear to be easy to come by and I’m missing a lot of numbers – and crucially the “o’clock” sample.
I’ve also ordered a “Wave Shield” for my arduino with a plan to prototype a hardware speaking clock. We’ll see if I get any further with that than I have previous arduino projects. They tend to fall apart when it gets to writing the software – I lose interest because it becomes too much like my day job ;)
Today:
Todays *major* excitement was that I went to a car boot sale, and bought these for £3
They may look like a pair of long nose pliers to most people – but they’re BT /GPO “81′s” (or “Pliers, Wiring, No2″ if I remember correctly, they’re usually just called 81′s) and they’re the *right* pliers for working on telephone equipment.
I’ve been looking for a pair for about 2.5 years and I’m absolutely stoked that I’ve now got some!
One of the chaps I work with at the Dean Forest Railway found this in his garage. As far as we can tell, it’s a callsender for generating simulated traffic in a telephone exchange. We don’t have any more information than that at this stage, and would really like a schematic or even just a pinout for the connector! If it can be made to do loop disconnect dialing (which somehow given its age I doubt) it might even be useful!
