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GCA123 LocoNet® switch panel


By Peter Giling


Have you ever been in the situation, sitting under your nice modelrailroad layout?
And did you then realise did you coudn't reach to the central to command a not very well funtioning turnout?
Of course there are nice options in LocoNet® with RocWeb, but it needs equipment like mobile phone.
The other option is to take the central station (IB, CSx or whatever) with you down under, but that unit is mostly fixed so that's not easy as well.
This is another option.
Using the same drawing of an GCA50, and adding 16 pushbuttons to it, that's all.
This GCA123 fits in the same box as GCA124 FredI.
Configuration is done in the same way as in GCA50.
The input numbers on GCA123 are numbered counter clockwise, starting top left.
The green led top left shows that power is on.
The red led top right shows LNet activity.
The used cable is a 6 wire RJ12 cable, like in standard LocoNet®, and can be of any length, up to 25 mtr.

Other feature

Without the box, this unit could be used to fix inside a switch panel.
With only one three wire cable, you have 8 turnouts under your command.
For thicker boards, where the button on GCA123 is not long enough to reach through, other buttons with longer pushing rod are available.

The final result

Hardware files

Remarks for construction

To drill the holes for leds and buttons, use the empty pcboard.
See for how it is done in GCA124.
Alle buttons, two leds, the crystal and several small capacitors, are fix on bottom side of pcboard.


The used firmware is exactly the same as GCA50.

Settings in Rocrail

This programming example shows the settings for the first 8 turnouts.
Left buttons set turnout 1 - 8 thrown. Top = Turnout 1
Right buttons set turnout 8 - 1 straight. Top = Turnout 8

mgv123-en.txt · Last modified: 2020/02/03 19:52 by phg