RailBOX RB 2112 — Configuration Reference

Reference documentation for RailBOX RB 2112 (and related RB 21x0 / RB 2110) DCC function-car decoders for wagon lighting and accessories. This document is not tied to the BigFred or Loco runtime; it is intended as a future data source for decoder configuration.

Item	Value
Source	RB 2112 manual (PDF) (RailBOX)
Models	RB 2112 and family variants — 13-output (RailCom®), 14-output, 21MTC (12 + 2 via jumper)
Scope	Wagon lighting, output mapping, brightness, lighting effects, RailCom® easy configuration

Decoder highlights: DCC (NMRA) and DCC S-9.2.1.1, up to 14 function outputs (125 mA each), direction recognition (including analog), per-output brightness and effects, output-to-function mapping via CV bit tables, optional RailCom® auto-detection with RailBOX: Railroad Control.

Not included: motor control, sound, Wi-Fi — see railbox-rb23xx.md for locomotive sound decoders.

Hardware variants and limits

Address and programming

Output mapping (function keys)

Lighting effects

Brightness

Power-on behaviour and analog mode

Servo output

RailCom® easy configuration

Factory reset

A — Full CV table

1. Hardware variants and limits

1.1 Purpose

RB 21x0 / RB 2110 / RB 2112 decoders are intended primarily for wagon lighting in HO scale. Supported formats: DCC only (not Motorola, Märklin, or MFX).

1.2 Variants (from manual)

Variant	Outputs	Connector	RailCom®	Board size (approx.)
13-output	13	Wire pads	Yes	30 × 15 × 2.3 mm
14-output	14	Wire pads	No	27 × 14 × 2.3 mm
21MTC (RailCom®)	12 (+2 via jumper → I1/I2)	21MTC	Yes	26 × 15 × 3.2 mm
21MTC	12 (+2 via jumper)	21MTC	No	26 × 15 × 3.2 mm

The first seven outputs plus supply have duplicate pads on the reverse side of the PCB.

1.3 Electrical limits

Parameter	Value
Supply	12–20 V AC/DC or DCC
Standby current	~25 mA
Peak current	up to 1 A (total)
Per output	125 mA

1.4 Wiring notes

LED lighting: direct to decoder pads, LED strip, or factory LED board.
21MTC: for ROBO® wagons or other 21MTC-equipped models; jumper can map two outputs to I1 / I2.
Keep-alive capacitor: optional external capacitor improves lighting on dirty track (see manual wiring diagram).
Servo: requires external 5 V regulator (linear or DC-DC) and 1 kΩ resistor per servo (see manual).

2. Address and programming

Programming modes: Direct Mode (programming track) or PoM (programming on main).

CV	Name	Range	Default	Description
#1	Short address	1–127	3	Decoder address
#7	Software version	0–255	—	Read only
#8	Manufacturer ID / reset	0–255	13	Read: manufacturer code; write any value → factory reset (§9)
#17	Long address high byte	192–231	192	Long address with CV #18; enable via CV #29 bit 5
#18	Long address low byte	0–255	100	Long address low byte
#19	Consist / MU address	0–127	0	If > 0, speed and direction follow this address

CV #29 — address and configuration (selected bits)

Bit	Value	Function
1	2	Speed steps: 0 = 14/27, 1 = 28/128
2	4	Analog mode: 0 = DCC only, 1 = analog allowed
3	8	RailCom: 0 = off, 1 = on
5	32	Address type: 0 = short (CV #1), 1 = long (CV #17/#18)

CV #28 — RailCom configuration

Bit	Function
0	CH1 address broadcast: 0 = off, 1 = on
1	CH2 enabled: 0 = off, 1 = on
7	Automatic detection: 0 = off, 1 = on

3. Output mapping (function keys)

Unlike RB 23XX (which uses map.txt), RB 2112 maps physical outputs O1–O14 to function keys F0–F28 separately for forward and reverse direction using bit-field CVs.

3.1 Outputs O1–O7 (CV #120–#177)

Each CV configures one function for one direction. The 8 bits select the F0_F and F0_R headlight outputs plus outputs O2–O7.

Bit layout (matching the manual table header O7 O6 O5 O4 O3 O2 F0_R F0_F):

Bit	7	6	5	4	3	2	1	0
Output	O7	O6	O5	O4	O3	O2	F0_R	F0_F
Value	128	64	32	16	8	4	2	1

There is no “O1” on this bank — output 1 is split into the two dedicated headlight outputs F0_F (bit 0) and F0_R (bit 1).

CV	Function	Default	Active outputs (bits)
#120	F0 forward (FL)	1	F0_F (bit 0)
#121	F0 reverse (FR)	2	F0_R (bit 1)
#122	F1 forward	4	O2 (bit 2)
#123	F1 reverse	4	O2
#124	F2 forward	8	O3 (bit 3)
#125	F2 reverse	8	O3
#126	F3 forward	16	O4 (bit 4)
#127	F3 reverse	16	O4
#128	F4 forward	32	O5 (bit 5)
#129	F4 reverse	32	O5
#130	F5 forward	64	O6 (bit 6)
#131	F5 reverse	64	O6
#132	F6 forward	128	O7 (bit 7)
#133	F6 reverse	128	O7
#134–#177	F7–F28 forward/reverse pairs	0 (most)	Per-bit F0_F/F0_R/O2–O7

Factory highlight: F15 forward default 252, F15 reverse 252 — all outputs O2–O7 plus direction bits (wagon interior lighting preset).

3.2 Outputs O8–O14 (CV #190–#247)

Extended mapping for additional outputs. Bit fields include O8–O12 (and higher outputs on later CVs).

CV range	Functions	Notes
#190–#247	F0–F28 forward/reverse	Defaults mostly 0; F7 forward/reverse default 1 (O9); F8 default 2; F9–F11 defaults 4, 8, 16; F15 forward/reverse 31 (O9–O12)

Bit layout for O8–O14 table: bits map to O12…O8 per manual (CV #232–#247 for F21–F28).

Programming tip: Set the CV for the desired function and direction; write the sum of bit values for all outputs that should activate together.

4. Lighting effects

Each output has an independent effect CV. Range 0–120 (base effect + modifiers).

4.1 Effect CV assignment

Output	Effect CV	Default
1	#33	0
2	#34	0
3	#35	0
4	#36	0
5	#37	0
6	#38	0
7	#39	0
8	#40	0
9	#100	0
10	#101	0
11	#102	0
12	#103	0
13	#104	0
14	#105	0

4.2 Base effect values (CV #33 pattern)

Value	Effect
0	Light bulb (steady)
1	Flash frequency 1 (period in CV #49)
2	Flash frequency 1, reversed phase
3	Flash frequency 2 (period in CV #50)
4	Flash frequency 2, reversed phase
5	Short pulse (duration in CV #53)
6	First custom sequence (CV #60–#72)
7	Second custom sequence (CV #73–#85)
8	Servo mode

4.3 Effect modifiers (add to base value)

Add	Effect
+16	Smooth fade using time from CV #51
+32	Smooth fade using time from CV #52
+64	Smooth fade over fixed 500 ms
+128	Run custom sequence once, then stop

4.4 Timing CVs

CV	Name	Range	Default	Unit
#49	Flash period 1	0–255	100	× 10 ms
#50	Flash period 2	0–255	100	× 10 ms
#51	Fade time 1	0–255	10	—
#52	Fade time 2	0–255	50	—
#53	Single flash duration	0–255	1	—
#54	Custom sequence step time	0–255	1	—

4.5 Factory custom sequences

CV range	Content
#60–#72	First custom sequence (one byte per step); factory default `0xB5,0xFD,0x6F,…`
#73–#85	Second custom sequence; factory default `0xC7,0x9F,0xFF,…`

5. Brightness

Per-output maximum and minimum brightness (PWM floor/ceiling).

5.1 Maximum brightness

Output	CV	Default
1	#41	255
2	#42	255
3	#43	255
4	#44	255
5	#45	255
6	#46	255
7	#47	255
8	#48	255
9	#106	255
10	#107	255
11	#108	255
12	#109	255
13	#110	255

5.2 Minimum brightness

Output	CV	Default
1–8	#90–#97	0
9–13	#182–#186	0

Effective brightness scales between minimum and maximum CVs for each output.

6. Power-on behaviour and analog mode

6.1 Output state after power-on (CV #55)

CV #55	Behaviour
1 (default)	Remember output states from before power was removed
0	Do not remember — outputs start from default mapping

6.2 Analog mode default function states

When analog operation is enabled (CV #29 bit 2), default function states on entry:

CV #13 — analog mode 1, F1–F8:

Bit	Default	Function
0	1	F1 on
1–7	0 / 1 per manual	F2–F8

CV #14 — analog mode 2, F0 and F9–F12:

Bit	Default	Function
0	1	F0 forward on
1	0	F0 reverse
2–5	0	F9–F12

7. Servo output

Set the target output's effect CV (§4) to base value 8 (Servo mode). External 5 V supply and 1 kΩ series resistor per servo are required (manual § wiring).

8. RailCom® easy configuration

Decoders marked with the RailCom® symbol support bidirectional communication with RailCom-capable command stations and the RailBOX: Railroad Control app.

8.1 Features (with RB 1110 central)

Automatic detection of new decoders on the layout and automatic address assignment
PoM read/write at any time on the main track
Short decoder name for identification in the app

8.2 Short name and metadata

CV	Range	Default	Description
#257–#264	ASCII	"WAGON"	Short decoder name (8 characters)
#265	0–255	0	Photo number low byte
#266	0–255	0	Photo number high byte
#268	bit field	0	Bits 4–7: decoder symbol type

CV #268 device type (bits 4–7):

Value	Type
0	Turnout
1	Semaphore
2	Turntable
3	Lighting (wagon)

8.3 RailCom CV summary

CV	Relevant bits
#28	Bit 0 CH1 address TX; bit 1 CH2; bit 7 auto-detection
#29	Bit 3 RailCom enable

9. Factory reset

Method	Value
Write CV #8	Any value triggers factory reset to defaults

After reset, re-program address (CV #1 / #17–#18 / #29) and output mapping as needed. Use --preserve-addr with loco prog factory-reset to keep the current address (RailBOX family: CV #8 = 1 in the Loco CLI implementation for RB23xx; RB 2112 manual states any CV #8 write resets).

Appendix A — Full CV table

Condensed from the manufacturer PDF. Output mapping detail: §3.

Address and identity

CV	Range	Default	Description
#1	1–127	3	Short address
#7	0–255	—	Software version (read)
#8	0–255	13	Manufacturer / factory reset
#13	bit field	—	Analog mode 1, F1–F8 defaults
#14	bit field	—	Analog mode 2, F0r/F0f, F9–F12
#17	192–231	192	Long address high
#18	0–255	100	Long address low
#19	0–127	0	Consist address
#28	bit field	—	RailCom configuration
#29	bit field	—	Speed steps, analog, RailCom, long address

Lighting effects (outputs 1–14)

CV	Output	Range	Default
#33–#40	1–8	0–120	0
#100–#105	9–14	0–120	0

Brightness

CV	Output	Range	Default
#41–#48	1–8 max	0–255	255
#90–#97	1–8 min	0–255	0
#106–#110	9–13 max	0–255	255
#182–#186	9–13 min	0–255	0

Effect timing and sequences

CV	Default	Description
#49	100	Flash period 1 (× 10 ms)
#50	100	Flash period 2
#51	10	Fade time 1
#52	50	Fade time 2
#53	1	Single flash duration
#54	1	Custom sequence step
#55	1	Remember outputs after power loss
#60–#72	factory	Custom sequence 1
#73–#85	factory	Custom sequence 2

Output mapping

CV range	Maps
#120–#177	F0–F28 ↔ outputs F0_F, F0_R, O2–O7 (forward/reverse pairs)
#190–#247	F0–F28 ↔ outputs O8–O14 (forward/reverse pairs)

RailCom® naming

CV	Description
#257–#264	Short name (ASCII), default `"WAGON"`
#265–#266	Photo index
#268	Decoder symbol / type

Relation to Loco CLI

Feature	RB 2112 support in Loco
Detection (CV #7 / #8)	Wagon reports CV #8 = 13 (factory default per manual); locomotive RB 23xx uses NMRA 172
`loco prog factory-reset`	CV #8 write — value 1 for RailBOX family in Loco CLI
`loco prog mapping set`	CV #120–#177 / #190–#247 bit tables (F0–F28, both directions by default). Outputs: `F0_F`, `F0_R`, `O2`–`O14` (output 1 is split into `F0_F`/`F0_R`, so `O1` is not accepted)

Mapping examples:

# Headlights: front light on F0 forward, rear light on F0 reverse
loco prog mapping set F0 F0_F --forward
loco prog mapping set F0 F0_R --reverse

# Map F2 to interior outputs O3 and O5
loco prog mapping set F2 O3,O5

| loco prog brightness | CV #41–#48 (O1–O8), #106–#110 (O9–O13); output O14 has no max-brightness CV in manual |