RC Train (IR)
A battery box with an infrared receiver inside a LEGO City locomotive, sold in two generations that cannot hear each other: 2006, then 2009 onwards. The 2006 pair listens on the 76 kHz carrier, everything from 2009 on listens to Power Functions at 38 kHz.
Reach
| Capability | State | Note |
|---|---|---|
| 7938, 7939, 3677 driven from the bridge | works, untested here | An ordinary Power Functions receiver: four channels, two outputs, seven speed steps each way |
| 7938, 7939, 3677 from the Speed Remote 8879 | works | The pairing the sets shipped as |
| 7897, 7898 from the bridge | out of reach | 76 kHz is a hardware ceiling for the emitter |
| 7897, 7898 from any other LEGO handset | out of reach | The 2006 handset speaks its own family and nothing else |
What it hears
The 2006 sets sit in the short-lived 76 kHz family together with Spybotics, Bionicle Manas, RC Nitro Flash and the DUPLO Dozer — about a year of sets, arriving a year before Power Functions did, and then dropped; the carrier and the channels are in 76 kHz IR family. From 2009 the trains are plain Power Functions (IR) receivers and answer the same 38 kHz messages as the 8884 does, timings and nibbles in Power Functions RC (IR). Both carriers are one way, so no train of either generation reports anything back. Older 9V trains with a speed regulator like 4559 are wired: no radio, no light.
Reaching it today
For a 2009 train: the Speed Remote 8879 if it came in the box, otherwise the bridge, which drives it like any other Power Functions receiver — pick the channel, pick the output, drive.
For a 2006 train: its own handset. Anything else has to modulate at 76 kHz, which is what puts the bridge out of range — see 76 kHz IR family.
Links
- 2006, 76 kHz: 7897 Passenger, 7898 Cargo. 2009 onwards, Power Functions: 7938 Passenger, 7939 Cargo, 3677 Red Cargo, with the Speed Remote 8879. See Sets & bricks index.
- Power Functions code, the same for a train as for any receiver: Arduino-PowerFunctions · community train write-up.
- Carriers side by side: Frequencies & wavelengths · How the links work.
- The 2006 carrier decoded: O Falcão, Decoding old LEGO infrared protocol — ofalcao.pt.