Converting an old analogue phone to VoIP, part 1 of N

Telephone Model 70, made by Autophon, 2. Dezember 1983.

Some time mid last year (Corona year 2020), I picked up an old analogue push button phone, from a Brocki (Brockenhaus) nearby. I think I paid something like 15 or 20francs. Not sure why, it just looked at me and begged me to “take me home”, I suppose 🙂

At first I just left it in the office on a shelf, not having any immediate plans for it. Being an old analogue phone, connecting it to our VoIP telephone system would not be possible, except perhaps with an A/D converter – so I slow began contemplating maybe converting it to VoIP. It seemed it ought to be perfectly feasible with a Raspberry Pi or some such, the inner electronics of an analogue phone are not overly complicated.

By December time, the idea had begun to take some shape. I had tried out the receiver, by connecting it to a USB sound “card”, one of those with a CM108 chip. I had also tried hooking the phone up to an A/D converter, a Linksys SPA2102. As the model 70, at least in this version, uses pulse dialling, that did not go very far. I had also studied other people’s conversion projects, e.g. Convert a rotary phone to VoIP using Raspberry Pi and Dette er en IP telefon or AS Elektrisk Bureau, both of which made it clear that I was not on some wild goose chase.

Nanopi Neo Air, side 1

Because the Raspberry Pi had been chosen for at least two such conversion projects, it had to be an obvious candidate for mine too. I also had a couple of Raspberries not being used for anything. On the other hand, I am not really a fan of the Raspberry Pi, I find it is too bulky and that there are many other smaller ARM boards that do a better job, in particular the Nanopi Neo Air, which I have used for a few projects in the past. When I realised that (a) the Raspi would need an external sound card whereas (b) the Nanopi had a built-in audio codec, directly accessible via four PCB headers, the choice was even easier.

After also verifying that the receiver could be connected directly to the audio codec pins, i.e. without any intermediate circuitry, the hardware choice was decided. Software-wise, I picked openSUSE Leap 15.2 as the basis. openSUSE has long been my go-to distro for everything I do, so that was easy too. On the telephony side, I had to go do some research, but it didn’t take me long before I settled on Linphone. For interfacing the miscellaneous hardware bits with the Linphone SDK, I planned on writing a small finite state machine in C. For configuration, I plan to run a small http server (thttpd).

From the beginning, my objective for the exercise was quite clear – the phone had to retain its retro 70/80s look and operation, yet have modern day VoIP functionality. Adding the OLED display does violate this idea somewhat, but I think it fits in quite well.

Posted in IT stuff | Tagged , , | Leave a comment

True luxury

When we go away for our annual summer holidays, we usually arrange with friends to take us to Bahnhof Erlenbach to catch the S-Bahn to the airport. Something similar on the return. Going to and from the airport with the S-Bahn is really quite easy and comfortable.

However, this time on the way out, Pascal Schweiger from Swiss Car Concierge took us to the airport. When you’re not traveling for business, being taken directly to the airport felt quite luxurious.

On the way back, first a night-time eight hour ferry trip and then a five hour early morning drive to Thessaloniki. A couple of days visiting the family, then back to the airport for a return trip to Zürich via Düsseldorf. In Zürich, we were met by Pascal in the luggage pick-up area.

Long story short, after a two week holiday and a somewhat arduous return journey, it was nothing less than sheer luxury to be met by Pascal in the airport and be taken straight home.

Full disclosure – Pascal Schweiger is a good friend of mine. I hope this posting might help improve his Google ranking.

Posted in Uncategorized | Leave a comment

Stupid password restrictions …

This has been getting up my nose for quite some time. Webmasters and/or webprogrammers that believe it is their duty to ensure my new account password is “secure” / “safe” / “hard to crack”.

  • must contain upper case and lower case characters,
  • must contain at least one numeric,
  • sometimes also a special character,
  • sometimes only special characters from a pre-defined set.

Webmaster, please keep your password restrictions to yourself!
For God’s sake, let me pick my password. It is absolutely none of your business, however well-intended!

On top of that, when you then fail to implement your restrictions properly, such as not letting me add special characters of my choosing or you won’t let me add a trailing space, that is just mind-bogglingly stupid!

By all means, do help people choose a good password, but don’t impose your restrictions on people who are quite capable to choosing a good password themselves!


Posted in Gripes | 1 Comment

ISDN, the end of an era

Both Swisscom and Deutsche Telekom have announced the end of ISDN support. In Switzerland, Swisscom plans to migrate all existing ISDN customers to all-over-IP by the end of 2017.

This really means the end of an era for me. In the 80s, I remember ISDN being installed in the bank where I worked, my first real job.

When I moved to Munich in 1992, my first telephone line was ISDN. At the time, it was the latest and greatest. With ISDN one had a 64kb dial-up line without blocking the telephone, even 128kb with channel bundling. In comparison to the prevalent 33.6K and later 56K (V92) analogue modems, even the basic 64kb offered by ISDN appeared to be light years ahead.

In 1997 I moved to London and obviously asked British Telecom to have an ISDN line installed. At first this was met with “what?”, then I figured out it was referred to as “BT Highway” and we were off. Later on in Zürich, Switzerland in 2001, ISDN was obviously my first choice again. At the time, ADSL was only just slowly beginning, and due to a poor connection to the local exchange, ADSL was initially not an option for me. Later on when ADSL technology improved, the internet connection moved to ADSL, but telephony remained on ISDN.

In 2004 when I founded my own company, obviously our telephone system was ISDN. We ordered a new line, Swisscom came and installed four. Both our private line and the business lines were easily plugged into the same 4-port ISDN card in the Asterisk server.

So ISDN has provided my telephone and internet services for the last 20 years. Deeply integrated into my private and business life, but usually hiding unseen in the back. Of course nne should not get so attached to an otherwise invisible technology, but I can’t help thinking it’s the end of an era.

Well, we still have two years, perhaps even more. Sofar Swisscom has not announced any actual migration plans, but I won’t wait and see. If we’re moving to VoIP, there are many options to be explored.

Posted in Uncategorized | Leave a comment


This is a very simple blog entry. If you are a real person with a genuine comment, please do not post it here.
Since I started this site, I have been receiving a steadily increasing amount of WordPress spam. Please continue, it is very useful.

Posted in Uncategorized | Leave a comment

Moving to MythTV

I’ve long meant to take a closer look at MythTV, but I’ve never really had the time nor the hardware, so it’s been just another project waiting in the pipeline. Besides, we’ve had a Nokia PVR for over ten years, so I’ve never had a real need either.

Nokia Mediamaster 9902S

However, in late October 2012, our ancient Nokia Mediamaster 9902S finally decided to pack it in. It had been acting up in the afternoon, refusing to accept a programmed recording, but when we got back from having dinner at a friend’s place, it plainly refused to do anything at all. We’ve had the Nokia Mediamaster since 2001, so eleven years and a few months. For consumer electronics, that’s probably longer than expected, so I can’t complain. To be honest though, it has at times been a love and hate relationship with the Nokia, but when it gave up last night and replacing the harddisk this morning did not provide any improvement, well, it was the end of an era.

Hauppauge WinTV Nova-S Plus

Anyway, enough about the Nokia, let me get back to the main topic. Earlier this year, probably around April, I did some experiments with MythTV as I had acquired a number of Hauppauge DVB-S receiver cards. Due to priorities, I didn’t get very far, but it did more or less work.

With the Nokia now dead and the family without television, I quickly hauled a couple of PCs into the livingroom and got a MythTV backend+frontend setup running. Sunday evening we watched television on a laptop, fed by the MythTV backend! This was very encouraging, so over the next three weeks I continued to improve on the setup:

IBM Thinkcentre 8212

The MythTV frontend ended up on a suitably quiet IBM Thinkcentre 8212, a small form factor desktop PC. (I had picked up some of these for another project a while back). With a 2.5″ harddisk from a laptop, it makes virtually no sound at all. The MythTV backend box is another IBM Thinkcentre, but full size. It’s really a bit bulky, but it has the needed PCI slots for the DVB-S receiver cards. In my earlier experiment I had equipped it with an elderly 300Gb Maxtor drive, but it was really a bit too noisy, so I replaced it with a 3Tb SATA Western Digital harddisk, that ought to be sufficient for a while 🙂

Our ageing Bang&Olufsen TV set, a ten year old Beovision 1, also finally got replaced – it only had S-video, SCART and coaxial inputs, none of which I could connect to the VGA output on the Thinkcentre. I had also long wanted to get a bigger TV, flat- and wide-screen etc., so this was the right opportunity. I ordered a new Toshiba 40″ with LED backlighting and a wall-mount.

Our existing satellite dish is unfortunately mounted on a Nokia Satscan motor, which is not DiSEqC compatible. I will eventually have to replace it I think, but as it is currently pointed at Astra 2 at 28.2°E, reception of english language TV (BBC, ITV, etc) is safe. To experiment with reception of German and Swiss TV, I was lucky to acquire a second satellite dish quite cheaply. After digging up otherwise long forgotten trigonometry, I got the second dish pointed at Astra 1 at 19.2°E and tuned into lots of German TV (ARD, ZDF, Pro7 etc). What is missing now is some Swiss TV. SFDRS broadcasts via Hotbird at 13°E, and I think I can get hold of that by using a dual-headed LNB.

Of course, in between fiddling with the hardware and looking after my day job, I also spent quite some time getting myself familiar with MythTV – the programme guide, recording, pausing, organising channel groups, making sure my DVB adapters always got the same numbering and so on. It’s not all very intuitive, so it will take some getting used to.

This weekend, now a full three weeks since the death of the Nokia, I re-arranged the aerial coax feeds and moved the MythTV backend into the back of the garage. It all went very smooth, no hiccups at all, so as of last night, we’re now enjoying evening entertainment courtesy of MythTV.

Posted in IT stuff | Leave a comment

New air-conditioning plant

Our Herrliberg datacentre is usually kept at a cool 20°C (currently klop°C). We could keep it higher to try to reduce energy costs, but due to the excellent insulation there is actually very little gained by raising the temperature threshold to e.g. 24 or 26. However, since April or May, the air conditioning has been straining to maintain the 20°C.
To be honest, I had noticed the average temperature creeping up towards 22°C, but as it wasn’t exactly critical, I pushed it back and more or less forgot about it. Until last week when I began running down my checklist for going away on vacation.

I had a thorough look at the airconditiong plant, and suddenly noticed that the R410A coolant was in fact slowly leaking! This is nowhere as bad for the environment as the old R12 (freon) coolant, but it’s very bad for the airconditioning efficiency. I called up the service company, who sent a maintenance guy the next day.

Quite clearly the outdoor plant was leaking coolant, but where? It wasn’t at any of the typical places – joints, connections etc. After some searching, it turned out to be the copper piping in the radiator. Unfortunately this meant there was no repairing it, it had to be replaced. I wasn’t exactly overjoyed – the plant is only just 3 years old, and of course the warranty expired only last year.

Regardless, this morning two guys from Baumgartner-Kälte showed up to replace the compressor-unit – they started at 8:20 and finished at 9:40, not bad at all.

Posted in Uncategorized | Leave a comment

FOSS Project Management

Within the openSUSE Community, the topic of resource planning and project management appeared and was discussed in mid-to-late June 2012. Due to factors largely outside the community’s control (hardware issues, the poor state of Factory), the planned release-date of openSUSE 12.2 simply could not be met.
As part of the discussion surrounding that, the possibility of a change of development strategy was brought up, see Stephan Kulow: Calling for a new openSUSE development model.
In the ensuing debate it was suggested that we apply traditional resource planning and regular project management. Almost immediately, this was met with sarcasm and ridicule, suggesting this was simply a ludicrous idea and quite impossible in a FOSS environment.

I disagree, I believe it is entirely possible to apply (at least some of) traditional project management to a FOSS project, in particular a Linux distribution such as e.g. openSUSE.

The three key factors

Traditional Project Management is largely about juggling three key factors:

  • resources
  • deliverables
  • deadlines

Experienced project managers will want add another 20 factors, but let’s ignore those for now.

The simplified view

In typical project management, two of the three key factors above are given, and it is the project manager’s first job to come up with the third factor:

  1. the resources and the deliverables are given, work out the deadlines.
  2. the deadline and deliverables are given, work out the resources.
  3. the resources and the deadlines are given, work out the deliverables.

Throughout the project’s lifetime, deliverables might change, deadlines might slip, and resources might come and go, so it is the PMs job to readjust factors and make predictions about deadline slippage, decisions about scope-limitation, applications for more resources etc.


  • if the resources change (somebody leaves the project), but the deadline has to be met, the deliverables have to change.
  • if the deliverables are changed upward, but the resources remain fixed, the deadlines have to change.
  • if the deadline is moved forward, but the resources remain fixed, the deliverables have to change.

And so on and so forth.
As mentioned above, many other factors could come into play – company politics, priorities, money etc.

FOSS Project Management is somewhat different to the above – primarily because the resources are not only not fixed, they are largely unknown and largely voluntary. Secondly because the PM is also (well, at least partially) charged with keeping the volunteer resources (i.e. the community) happy and motivated.

PM Model #1: let the deliverables be the constant factor and vary the deadlines according to the progress made.
PM Model #2: let the deadlines be the constant factor, and let the deliverables vary according to the progress done.

So far, openSUSE has been working with model #2 – a fixed release schedule and varying the deliverables according to that. For openSUSE 12.2, it became clear that the deliverables could simply not be ready on time, regardless of how much they were reduced. Essentially we are now looking at model #1.

Model #1 requires us to measure progress. I suggest that this might be possible by having many and simple (i.e. easy to measure) milestones.

openSUSE current milestones

We have long had the typical set of software project milestones – alpha release, beta release, release candidate 1, maybe a release candidate 2, then Gold Master. Because of openSUSE working according to model #2, those names were actually largely irrelevant. They indicated only deadlines, not deliverables. Due to the varying resources, it was impossible to tell exactly what state the distribution would be in at a given time, so there was no real meaning to the term “alpha release”. It was simply a snapshot on a given date.

If we are to change to model #1, we need to define the deliverables, thereby hopefully adding real meaning to e.g. “alpha release” and “beta release”. To be able to measure progress and state of the deliverables, these would be made up of a set of fine-grained, easy-to-gauge milestones. When for instance 80% of a set of milestones have been met, the deliverable would be 80% complete. The time it took to get thus far could be used to extrapolate the time it would take to complete the remaining 20%. Of course, this is guesstimating at best, but I think it would give us significantly improved control and much better visibility.

There are a few more topics that I ought to discuss here:

  • defining deliverables
  • defining milestones
  • measuring progress

However, I’ll leave those empty for now. I really just wanted to argue that it is entirely possible to apply traditional project management in a FOSS environment/project.

Posted in openSUSE | Leave a comment

Five years of running Asterisk and VoIP

In my business, we receive faxes via Asterisk and Hylafax, which send them to a dedicated email-address. We don’t really receive many faxes, certainly no more than one or two per week. Today I was just checking to see if the email folder needed to be tidied up, and happened to notice that the first fax received was dated 27/3/2007. That is almost exactly 5 years ago which is as long as the telephone system has been running Asterisk.
Actually a bit more than 5 years – I remember setting up the Asterisk box over Christmas 2006. My business was beginning to gain some momentum, we had just hired the first salesman, and it was critical that I got his home-office hooked up with a VoIP telephone.

Anyway, 5 years of running VoIP with Asterisk!

Posted in Uncategorized | Leave a comment

FTTH – we’re online!

Slightly late update, but as of last Friday 23/3/2012, we have fibre-optic internet access! My provider called up in the morning to say “never mind about the VLAN, we’re skipping that, just use plain DHCP to get an address.”. Sure, no problem. When the electrician was done installing the fibre-to-copper converter, I hooked up my laptop et voila!
I’ve arranged with the provider that I have two-three weeks to test/verify everything, after which I’ll be switching the company network over from ADSL to fibre. To start with, I’ve only ordered a 50/10Mbit connection, but when compared to the current ADSL connection, that is almost 10 times more downstream and more importantly, almost 20 times more upstream bandwidth.

The fibre-to-copper converter/switch and the two optical terminator boxes.

I’m slightly worried about the fibre-to-copper converter or switch. It has 8 ethernet ports and 1 fibre port, and looks a lot like a Zyxel box. It has a distinct consumer look&feel, which makes me a little uneasy. I’ll have to check the manufacturer, I really hope it’s not a Zyxel box.

Posted in IT stuff | Leave a comment