Up the Creek Column - 9
I also thought that at some point I might need multiple con-
trol panels. For cases where an op session was short-handed
and I needed one operator to take on the duties normally
performed by two, each semaphore could be controlled by
multiple train order panels.
The Tam Valley schematic called for three push buttons to
operate each semaphore blade or six for one train order mast
(17a). I had some rotary switches on hand and figured that by
using them I could reduce the switch count to a rotary switch
and two push buttons (17b).
Up to this point things had gone pretty well. But once I hooked
up the Oakhill panel nothing seemed to work right.
Troubleshooting the panels
The first problem I had to deal with was my own fault (aided
and abetted by Radio Shack). I found the drawer with the
switches at my local Radio Shack, located the bin for the nor-
mally-open push buttons, checked the label on a package – it
said normally open, and grabbed two packages. I should have
checked the second package from that bin. Apparently Mr.
Murphy, the store manager, had mixed normally-open and nor-
mally-closed switches in that bin.
I wasted a lot of time figuring out why my semaphore blades
changed position as I twisted the rotary switch without a but-
ton being pressed. Eventually I had an "aha" moment and
realized that normally-closed push button switches had snuck
into my control panel. After installing the correct switches the
semaphore behaved a bit better. But the semaphores some-
times still followed twists of the rotary switch.
