Recently, I’ve found an easy way to switch the isolation and pro-
gramming tracks and get a readout of what you are doing. I show
the schematic diagram for those who relate to those things. I
didn’t show the programing track booster (PTB) or the wall-wart
to power the relay in the schematic. There is a block diagram later
for those of you who don’t relate to schematics.
Parts List
QTY ITEM
DIGIKEY PART NUMBER
1 Relay - 4PDT with 12 volt coil HJ4-‐DC12V
1 Miniature SPST switch
M2011SS1W01/UC
1 Rectifier
1N4001-‐G
2 Resistor 1 K ⅛ watt or larger CF18JT1K00
1 LED red
C503B-‐RAS-‐CY0B0AA1
1 LED green
WP710A10GD
This parts list is not extensive, as it doesn’t include the PTB or
the wall-wart power supply. I included Digi-Key part numbers,
but most, if not all can be purchased from surplus stores, like All
Electronics. The relay listed has 5 amp contacts. Larger systems
will need a bigger relay 10 - amps.
When the switch is open, the power is not applied to the relay
and the DCC power is applied to all the tracks and the green
LED is lit. Closing the switch applies the DC power to the relay
and it breaks contact with the DCC signal before it makes con-
tact with the programming track signal, whether directly from
the command station or through a PTB. The red LED will receive
power when the relay does, so
it will light. The 1N4001 diode
From Mr. DCC’s workbench
Isolating the programming track on
your layout
DCC Impulses Column - 8
MRH-May 2014
