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Railway extension module made by a Polish company - construction and interior

p.kaczmarek2  7 1803 Cool? (+4)
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TL;DR

  • Moduł Universal I/O Unit MPT z kolejowego sprzętu po dekomisji wygląda na polski projekt i pełni rolę rozszerzenia wejść/wyjść.
  • W środku są dwie płytki: zasilacz na L4978D, MCU H8/36057, konwerter ST232C oraz dopasowanie do magistral CAN i RS422 przez TJA1040 i SP491EEN.
  • Zasilanie wynosi 16–36 V, a pobór prądu dochodzi do 80 mA przy 24 V.
  • Obudowa jest mocno zgnieciona, więc uruchomienie może się nie udać, ale da się odzyskać inwerter oraz transceivery CAN i RS232.
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Black “PIXEL Universal I/O Unit MPT” module housing with a 12-position DIP switch and LED labels
Here's the inside of another 'railway' equipment after decommissioning. This time the casing is pretty much squashed, but it's still worth a look inside - what is the so-called 'technical measurement module'? The English name is Universal I/O Unit MPT, which suggests it's an expansion card of some sort.
Black metal PIXEL housing labeled “Technical measurements module” MPT 228.00, 16–36 V
Operating voltage is 16-36 V, current up to 80 mA (at 24 V). It looks, to me, like a Polish design.
We remove the cover:
PCB I/O module in a metal frame with connectors, a blue DIP switch, and a “Sprawny” label.
The centre resembles that of the GPS module shown earlier - we also have the programming connector and the LED display here, which has been hit quite hard. The boards here, however, are two.
Two green PCBs inside a black enclosure, with a DIP switch and a D‑Sub connector
The power section is based on the L4978D, which is a DC-DC converter that reduces the voltage.
“Typical Application Circuit” schematic for L4978 with inductor, diode, and capacitors
The coil has unfortunately also flopped.
Let's remove the top PCB:
Two PCBs from industrial electronics: main board with DB9 port and connectors, plus a smaller daughterboard
The coil, however, has also flopped:
Close-up of a PCB with ICs and a blue DB9 (RS‑232) connector
Here we see the main 16-bit MCU (H8/36057), the TTL-RS232 ST232C converter (from programming? This RS232 connector is not visible on the case), and the circuits from level conversion to the main communication bus (TJA1040 and SP491EEN), successively CAN and RS422. These lines are protected by PTC thermistors:
Close-up of a green PCB with capacitors, connectors, and a blue DB9 serial port
Two EEPROMs remain (with space for a third) - 24C04WP:
Close-up of a PCB with H8/36057 IC, crystal oscillators, and pin headers
And then there's the 74HC14D - inverter, Schmitt flip-flop, probably in the buffer role?
Close-up of a PCB with a microcontroller, ICs, SMD parts, and a black multi-pin connector
Bottom of PCB:
Bottom view of PCB labeled SIOM_UC1_v1 with SMD components and barcode sticker.

What remains is the IO overlay. From what I count, the connector on the outside is 2x12 and from the IO board is 2x13.
Close-up of the lower part of a green PCB with multiple ICs and a pin header
There is a single HC14 on the board, presumably in a buffer role. In addition to this we have 7 operational amplifiers 9221 (TS922IDT). There are 8 BSP75N transistors at the output:
Close-up of PCB with BSP75N transistors and SMD components
At the bottom we still have 0.50 A 60V LP60-050 polymer fuses:
Close-up of LP60-050 yellow polymer fuses on a green PCB with gold pin headers
It's difficult for me at the moment to make a fully reliable assessment of what the role of the TS922IDT is in this circuit. My guess is that it is the inputs. Is anyone reading able to supplement?

In summary , this was the IO module I received with a packet of 'railway' scrap, although I don't know exactly where it was used. The whole thing took a bit of a beating at checkout, so I don't know if I'll get it up and running, but the inverter at least I could recover, the CAN and RS232 transceivers will also come in handy. Interestingly, the whole thing has inscriptions in Polish, even on the PCB, so one could suspect that it was designed in our country.
If anyone has any additional information, feel free to comment.
About Author
p.kaczmarek2
p.kaczmarek2 wrote 14387 posts with rating 12308 , helped 650 times. Been with us since 2014 year.

Comments

J_Bravo 24 Jan 2026 12:53

Equipment sold by Pixel Bydgoszcz manufactured by SiMS Bydgoszcz. Mounted to passenger information system in public transport. Very solid. Virtually indestructible, but difficult to service. [Read more]

vania 24 Jan 2026 21:27

https://obrazki.elektroda.pl/3349287000_1769286157_thumb.jpg And what designation does this circuit have? Just asking out of curiosity. There is a similar one in the post about GPS Could there... [Read more]

p.kaczmarek2 24 Jan 2026 22:00

And fact, I was also supposed to give a photo after peeling off. https://obrazki.elektroda.pl/7559417500_1769288289_bigthumb.jpg F16V8BQL - PLD, Programmable Logic Device. [Read more]

Neorecormon 25 Jan 2026 22:03

Hello, as to the presented device : "There is a single HC14 on the board, probably in the role of buffer. In addition, we have 7 operational amplifiers 9221 (TS922IDT). There are 8 BSP75N transistors... [Read more]

p.kaczmarek2 25 Jan 2026 22:11

Thanks for the clarification. There is indeed more hidden in their catalogue note than I thought: https://obrazki.elektroda.pl/5990818800_1769375398_bigthumb.jpg https://obrazki.elektroda.pl/5468649400_1769375450_bigthumb.jpg... [Read more]

Neorecormon 26 Jan 2026 19:41

If you have any questions about devices for rail and automotive then write PW. I have been designing electronics for automotive and rail for several years. So I know this and that :) [Read more]

Galareta 17 Feb 2026 20:29

Interesting, an integrated driver and additionally a polymer fuse. Well, someone has protected themselves. [Read more]

FAQ

TL;DR: Polish Universal I/O Unit MPT teardown: 16–36 V input, ~80 mA at 24 V; “Operating voltage is 16–36 V.” [Elektroda, p.kaczmarek2, post #21818045]

Why it matters: This FAQ helps repairers identify parts, power safely, and reuse components from decommissioned public-transport modules.

Quick Facts

What is the Universal I/O Unit MPT and where is it used?

It’s a technical measurement/expansion I/O module used in public transport passenger information systems. J_Bravo reports it was sold by Pixel Bydgoszcz and manufactured by SiMS Bydgoszcz. He adds it’s very solid and difficult to service. “Virtually indestructible, but difficult to service.” [Elektroda, J_Bravo, post #21818170]

What are the safe power specs for bench testing?

Power it from 16–36 VDC. Typical draw is up to about 80 mA at 24 V. The input converts down through an L4978D buck stage. Confirm no shorts before applying power. This statistic and architecture come from the teardown photos and notes. [Elektroda, p.kaczmarek2, post #21818045]

Which processor and memories are on the board?

The main controller is a Renesas H8/36057 16‑bit MCU. Non‑volatile storage uses two 24C04WP EEPROMs, with space for a third device. These appear on the main PCB adjacent to the comms transceivers and logic. [Elektroda, p.kaczmarek2, post #21818045]

What communication interfaces does the module expose?

It carries a TJA1040 CAN transceiver and an SP491EEN RS422 transceiver as the main buses. A ST232C provides TTL‑to‑RS232 conversion, likely for programming. The bus lines include PTC protection elements. [Elektroda, p.kaczmarek2, post #21818045]

What does the I/O daughterboard contain?

The I/O overlay shows one 74HC14 buffer, seven TS922 op‑amps, and eight BSP75N output transistors. Output protection uses LP60‑050 polymer fuses rated 0.50 A at 60 V. This mix suggests analog conditioning plus low‑side or high‑side switching. [Elektroda, p.kaczmarek2, post #21818045]

Is there a programmable logic device on this unit?

Yes. The masked device under the label is identified as an F16V8BQL PLD. This answers the query about a possible GAL‑class part. It sits near the MCU and bus interface area. [Elektroda, p.kaczmarek2, post #21818756]

How rugged is the hardware in service?

A contributor with field experience calls it very solid and almost indestructible. However, he notes serviceability is challenging due to construction. Expert note: “Virtually indestructible, but difficult to service.” [Elektroda, J_Bravo, post #21818170]

What are common damage points to inspect after decommissioning?

Check the power inductor and LED display first. The teardown shows a collapsed coil and a struck LED display, plus a squashed casing. Inspect these before applying power to avoid secondary failures. [Elektroda, p.kaczmarek2, post #21818045]

Which connectors and pin counts should I expect?

Expect a 2×12 external connector and a 2×13 interconnect to the I/O board. Verify continuity and inspect for bent pins or cracked solder joints before reuse. [Elektroda, p.kaczmarek2, post #21818045]

Can I reuse parts if the module is beyond repair?

Yes. The inverter stage, CAN transceiver, and RS232 transceiver are recoverable and useful in other projects. Salvage after confirming parts are electrically intact. This advice comes directly from the teardown author. [Elektroda, p.kaczmarek2, post #21818045]

What protects the communication and output lines?

Bus lines include resettable PTC thermistors. Outputs are fused with LP60‑050 polymer fuses rated 0.50 A at 60 V. This combination reduces fault currents and helps the board survive wiring errors. [Elektroda, p.kaczmarek2, post #21818045]

How do I power up and probe the module safely? (3‑step)

  1. Inspect coil, LED display, and casings; repair visible damage.
  2. Feed 24 VDC within the 16–36 V range; monitor current (≤ ~80 mA).
  3. Observe activity on CAN/RS422 lines; use the programming header via the ST232C interface if needed. [Elektroda, p.kaczmarek2, post #21818045]

Who labeled or designed the PCB?

Silkscreen and labels are in Polish, suggesting domestic design. The author notes Polish inscriptions even on the PCB. Coupled with field comments, this aligns with a Polish supply chain. [Elektroda, p.kaczmarek2, post #21818045]

Who built and supplied these units to operators?

According to field feedback, Pixel Bydgoszcz sold the equipment, while SiMS Bydgoszcz manufactured it. The units were mounted in passenger information systems on public transport. [Elektroda, J_Bravo, post #21818170]
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