RC Train (IR)

RC Train refers to LEGO's infrared remote-controlled trains, which span two distinct and incompatible IR generations.

Early RC Train — 76 kHz (2006)

The 2006 9V RC Train system — 7897 Passenger and 7898 Cargo — uses the short-lived 76 kHz IR protocol (the same family as Spybotics, Bionicle Manas, RC Nitro Flash, DUPLO RC Dozer). It predates Power Functions (2007) and was quickly abandoned; its remote does not interoperate with PF. (Source: O Falcão — decoding old LEGO IR lists 7897 among the 76 kHz devices.)

Later City trains — Power Functions (38 kHz, 2009+)

The later City trains (e.g. 7938 Passenger, 7939 Cargo, 3677 Red Cargo) switched to the 38 kHz PF protocol driven by the PF IR Speed Remote 8879 — channels + speed steps. These are the well-supported ones today (Arduino libs, micro:bit, etc.).

⚠️ Note: older 9V trains (e.g. 4559 speed regulator) are wired, not IR — not relevant here.

How to control today

• 38 kHz PF trains → Arduino-PowerFunctions, micro:bit PF sender, community train projects (arduinolegotrains).
• 76 kHz early train → 76 kHz IR family tooling.