How easy is it to paralyze the Polish railroad? Let's find out!

In recent days, there has been a peculiar "trend" of emergency stopping of trains using radio-stop signals. Not for the first time and probably not for the last, but this time the situation is interesting in that there is an ongoing war abroad, and various politicians are trying to "connect" themselves to these actions with their speeches, often speaking untruthfully. So, let's see what the reality is.

I just woke up from hibernation... What actually happened?

In the past few days, "someone" maliciously caused trains to stop abruptly in various locations in Poland. How – we'll get to that in a moment. The significant thing is that this is not happening for the first time – quite the opposite, such "antics" have been taking place quite regularly, for a long time now. It was written about by Niebezpiecznik, for example, in 2010 and 2011. Between these articles, another wave was described by TVN24, and a considerable wave of such incidents also occurred in 2021.

This time, the attacks are even more amusing, as besides the radio-stop signals themselves, someone was also broadcasting... the Russian national anthem and a fragment of Putin's speech over the radio.

Unfortunately, due to this situation (and probably because of the ongoing war in Ukraine), politicians are getting involved and trying to escalate the situation – for example:

Why are we writing about this?

We dislike lies and manipulation. We believe that even the harshest truth is better than the best lie. Unfortunately, discussions on the Internet, fueled by statements from politicians, such as the one above, typically head in the direction of "how to prohibit this," or "doing this requires specialized knowledge." That's why we felt obligated to present what radio-stop signals exactly are, how simple it is to transmit them, and whether it can be effectively prohibited.

So, what exactly is this radio-stop thing, and why does it even exist?

The radio-stop function is a mechanism used for remote emergency stopping of trains before a collision, derailment, or other catastrophe occurs. It can stop any train in Poland by simply sending an appropriate radio signal, which will be received by electronic devices in the locomotive.

The first difficulty lies in the fact that different routes use different radio frequencies. In general, there are 7 "operational" channels and 3 additional ones used:

1. 150.100 MHz

2. 150.150 MHz

3. 150.225 MHz

4. 150.325 MHz

5. 150.375 MHz

6. 150.450 MHz

7. 150.575 MHz

8. 150.500 MHz

9. 150.200 MHz

10. 150.350 MHz (channel for device testing)

So in order to transmit anything effectively, one needs to know first which channel is used on which route:

Alright, we have the frequency and the route. But what exactly needs to be transmitted?

The radio-stop signal consists of 3 acoustic tones – sequentially 1160 Hz, 1400 Hz, and 1670 Hz. They should be transmitted in order for 0.1 seconds each, followed by a 0.5-second pause to activate the train's safety brake. This leads to a gentle deceleration.

The sequence can also be transmitted twice (without the 0.5-second pause) to induce sudden braking (much more thrilling for passengers).

Wait, what? Aren't these things supposed to be secret?

No, they are not.

More: Not only are they not secret, but they are actually officially described – among others:

• in European law – "The PKP Radio System"
• on the website of the Office of Electronic Communications (UKE):

Alright, is it difficult to transmit such a signal in practice? And is specialized equipment needed?

No, quite the opposite. It's a simple analog signal without any encryption or other protections – after all, it was meant to be a safeguard in unforeseen situations and needed to be as simple as possible, hence more reliable.

So, it can be transmitted using any radio transmitter that allows broadcasting on a user-selected frequency. An example of such a transmitter is the inexpensive Baofeng handheld radio – a note of caution: some of the Baofeng radios sold on platforms like Allegro might have certain frequencies blocked. However, you can buy the UV-5R model without restrictions. Alternatively, there are models with increased power up to 8W (which means greater range, theoretically up to 7 kilometers). Here's how it looks:

Well, can't these handheld radios draw attention in the field? Are there any other options?

Absolutely, but keep in mind the costs: a Baofeng handheld radio (or similar) is by far the cheapest and simplest method for executing such an attack, even if you have to figure out how to effectively camouflage or conceal it.

However, if you require better concealment or greater scalability, say for multiple simultaneous actions scattered across Poland, then a much better choice would be the so-called SDR, or Software Defined Radio. In essence, it's a device... nearly identical to the aforementioned Baofeng, but enclosed in a different type of casing and designed to work with a computer (without its own keyboard, display, and speaker, as the computer controls everything).

Of course, this "computer" doesn't necessarily need to be a full-sized computer – at least not always. It could be a Raspberry Pi or other inexpensive single-board computer (SBC), or simply a laptop.

Can you control these Baofengs and other SDRs somehow? Can't we just ban them?

First and foremost, using transmitting or transceiving devices without a permit is an offense and is subject to a fine of up to 1000 Polish zlotys, potentially along with the confiscation of the equipment used. This fine applies to broadcasting in general – if it involves intentionally paralyzing train traffic, the penalty could be much higher, especially with the recent amendment to the Penal Code approved by the Polish Parliament a few days ago.

Of course, there are frequency bands and transmitters that can be used without a permit (e.g., the 433 MHz band used by car remotes and other home electronics), but the 150 MHz band used by the Polish State Railways (PKP) isn't among them.

You can also legally use transceiving devices as long as you're not transmitting anything. And, of course, you can buy and possess such devices without restrictions.

But what if we were to ban these devices and effectively remove them from the market?

There are estimated to be several hundred thousand units of various shortwave communication devices in Poland – a large portion of which are used for communication between workers in rural and dispersed areas. Their purchase and use also don't require any form of registration.

If, theoretically, possession of such devices were suddenly banned, and confiscations began, there would still be a significant number of devices circulating in the second-hand market, enabling the harassment of Poles with radio-stop signals for years. So, that's not a viable solution.

Let's assume, though, that I'm a duckonian dictator* and I confiscate all the Baofengs – what then?

*This is a reference to the fact that in Poland, there isn't truly a president in power, but rather the leader of the ruling party, Jarosław Kaczyński, whose last name is directly associated with a "duck" (in Polish, "kaczka"). His actions directly resemble a dictatorship.

In that case, it's worth remembering that radio-stop is an analog signal on a fixed radio frequency – so constructing a simple transmitter from components readily available in any electronics store or even salvaged from practically any other device would be very straightforward. Let's take a look at how simple the schematic for such a device is:

What we have here:

Literally 2 transistors (BF199 and BC546, costing around 80 and 50 groszy (grosz (grosh) is like cent (1/100 of PLN), 80 groszy = 0,19 USD, 1 PLN (100 groszy) = 0,24 USD) each in retail)

• 2 pieces of coil – meaning literally a few dozen turns of enamel-coated wire, manually wound, perhaps on a pencil
• Several capacitors and resistors
• Electret microphone
• 9V battery
• Antenna, which is about a meter of wire

And that's it. After assembly, the whole thing might look something like this:

To make assembly easier – so that soldering isn't necessary – you can add a contactless universal board to it, for example, like this one:

However, this is just the first part – the radio transmitter. And what about generating tones? There are several possibilities:

Record them on a device and then place the speaker near the microphone – but then a second device is needed

Generate them from scratch on a computer – but then that computer is needed

Construct a simple tone generator independently

Ironically, an audio tone generator (especially multiple tones) is slightly more complex than a low-power radio transmitter. But still straightforward:

Given that we want to generate 3 different tones and switch between them at a rate too fast for a human, the easiest way to automate this is by using the incredibly popular integrated circuit, the NE555 (or simply 555 – it was produced under various designations by several different companies, and its various versions can be found salvaged from old televisions, alarm systems, or many other devices).

For clarity: the above schematic is purely illustrative. To generate tones for radio-stop, you will need at least 4 additional resistors – however, this schematic demonstrates how simple, almost primitive, the construction of such a device is. The saturation of Poland with various general-use electronics, from which all necessary components can be salvaged, is so vast that preventing the DIY assembly of such devices is absolutely unrealistic.

Do these simple devices have any limitations? What about range and signal quality?

Yes, the transistor models used intentionally have very low power and consequently a range that should reach around 35-40 meters in open terrain. You might consider increasing this range, but very cautiously (100 meters is rather unrealistic, let alone larger distances), as otherwise the transistors might burn out. Of course, you can use entirely different transistor models to extend the range to even a few kilometers, but:

• Higher power consumption leads to faster battery depletion – a well-constructed low-power transmitter can operate on a single battery for several weeks, whereas a handheld radio's battery might last for a maximum of a few hours
• A radio transmitter is a high-frequency device – it contains hard-to-detect interferences that we don't encounter in "classic" electronics. So, to achieve a greater transmission range while maintaining even minimal audio quality, it's not enough to simply increase the voltage – it's necessary to add more and more components to stabilize the circuit's operation and thereby address various issues. So, it's a trade-off: greater range in exchange for significantly more complex electronics. For comparison, here's a schematic of one of the older models of Baofeng:

A simple design also comes with other limitations:

• Very low audio quality of the emitted signal (only mono, noise, sensitivity to various types of interference, etc.) – sufficient, however, for emitting the radio-stop signal, especially when the tone sequence is looped
• Fixed frequency (adjustment requires manually stretching coil windings, which can be quite challenging in field conditions)
• The used universal board doesn't require soldering, allowing for very rapid prototyping and suitability for laboratory conditions, but such a constructed circuit is not resistant to any shocks or falls (in case of a fall, it will simply fall apart)
• There are different quality classes of basic electronic components such as resistors – the lowest-grade ones have a tolerance of up to 20%, meaning the real parameters of a specific component can deviate from the nominal values by up to 20% – this is practically corrected by incorporating a potentiometer (a resistor with adjustable resistance) into the circuit

Does all this mean that nothing can be done?

With the current system, indeed, there isn't much that can be done, as it lacks any built-in protections – that's why perpetrators of various "pranks" are usually identified only after the fact, often based on recordings from various cameras that have been manually matched to the time and place of the radio-stop signal reception.

However, effective protection against such pranks (or acts of Russian sabotage) requires transitioning to a much newer system called GSM-R (you can also read about it under names like ERTMS or TEN-T network). The implementation of this system was planned several years ago, but for various reasons, it has been delayed, and the current target for August 2023 is to implement GSM-R on... 42% of the entire Polish railway network by the year 2050.

So, for now, we have to get used to these pranks and hope that the authorities will efficiently catch the pranksters.