2. LocoNet electrical & command station wiring
Verify against the Digitrax LocoNet Personal Edition (LocoNet PE) specification before cutting copper. The values below reflect community practice; the LocoNet PE document is the normative source for line levels, timing, and the RJ12 pinout.
2.1 The LocoNet bus in one paragraph
LocoNet is a multi-drop, single data line, open-collector bus running at a nominal 16,660 baud (≈ 60 µs/bit) on the wire. Idle = line released high (pulled up by the master, ~12–15 V domain); a node transmits by pulling the line low. Several nodes can be wired in parallel with standard RJ12 patch cables; collision detection is done by listening while transmitting.
For this deployment:
- The Uhlenbrock 63120 handles wire timing internally — the Pi only sees 57600 baud on USB (LocoBuffer host link), not 16.660 kbaud on the wire.
- You still need correct RJ12 wiring and the throttle-side LocoNet port; the interface cannot fix a RailSync mis-wire or a dead bus.
2.2 RJ12 (6P6C) pinout
LocoNet uses a 6-pin/6-conductor (6P6C) modular connector. Typical assignment (confirm with a meter on your central):
| Pin | Signal | Notes |
|---|---|---|
| 1 | RailSync − | Track-level voltage — do not connect to Uhlenbrock 63120 logic |
| 2 | Ground | Logic ground |
| 3 | LocoNet data | Open-collector data line |
| 4 | LocoNet data | Same net as pin 3 |
| 5 | Ground | Logic ground |
| 6 | RailSync + | Track-level — leave unconnected on throttle branch |
The Uhlenbrock 63120 needs pins 2/5 (ground) and 3/4 (data) only.
2.3 Which socket on the command station?
Digikeijs DR5000 (two LocoNet sockets)
| Port | Purpose | RailSync present? | Use for Uhlenbrock 63120? |
|---|---|---|---|
| LocoNet-T (Throttle) | Handhelds, computer interfaces | No (or limited) | Yes |
| LocoNet-B (Booster) | Boosters, RailSync devices | Yes (track-level) | No |
Connect the Uhlenbrock 63120 to LocoNet-T with a standard LocoNet patch cable.
RailBOX RB1110 / RB1110-Mini
The central has a LocoNet RJ12 for handhelds and modules on the layout. For
BigFred, use z21 on LAN/WiFi instead — §7.
Do not use the Uhlenbrock 63120 on RB1110 for the supported hub path.
Other centrals
Use the port labelled for throttles / computer / LocoNet (not booster / RailSync-only). When in doubt, check the manual for RailSync on pins 1 and 6.
2.4 USB LocoNet on the central (optional alternative)
Some masters (notably DR5000) also expose LocoNet on USB as a virtual COM port (LocoBuffer stream). This document standardises on Uhlenbrock 63120 on the Pi so the central's USB stays available and the hub host is always the Pi (§1.6).
2.5 Power on the LocoNet side
| Device | LocoNet power |
|---|---|
| Uhlenbrock 63120 | Powered from the LocoNet bus (throttle-class) |
| 62280 (Luisa) | Optional repeater: 12 V / 500 mA on secondary segment |
Requirements:
- Command station on and driving LocoNet before expecting Uhlenbrock 63120 traffic.
- If the Uhlenbrock 63120 branch is long or heavily loaded, add 62280 between the central and the Uhlenbrock 63120 (see §4.5).
USB powers only the Uhlenbrock 63120 USB electronics; LocoNet line drivers still need a healthy magistrala.
2.6 Cabling & topology rules
- Use 6P6C LocoNet patch cables; daisy-chain or a distribution board.
- Keep stubs short; long unterminated branches degrade edges.
- Never wire RailSync into data pins.
- One RJ12 from Uhlenbrock 63120 to the LocoNet bus (through Luisa if used).
- One BigFred
dcc-busopener per Uhlenbrock 63120 USB serial port.
Continue with §3 Host platform.