MTH Signal Bridge and AIU/TIU

Without having a signal bridge in front of me, it sounds as if you are not wired correctly.

The signal bridge should have 3 wires for each pair of bulbs. One of these wires is a Common. Assuming you label the wires red bulb, green bulb and Common, putting voltage to red bulb and common should light the red bulb,  and putting voltage to green bulb and common should light the green bulb.

Assuming that you want the signal to be green by default, wire as follows:

• Red bulb wire to AIU Acc port "2"
• Green wire bulb to AIU Acc port "1"
• Acc port IN to transformer Hot
• Common wire to transformer Common.

The signal will come on green. When you activate it via the remote ON soft key, it will turn red. When you press the remote OFF soft key it will turn green again.

Barry, there are only three wires, as this is the MTH Pennsy Signal bridge with the amber lights in a vertical or horizontal pattern.

The instructions say to attach the red wire to ACC Port In, and the green wire to ACC port 1.

Which I did.

The ACC port is shown to be empty.

I just looked at the instructions for the "#30-11030 O Scale Pennsy Signal Bridge" and it's pretty much as I said. Below, I changed the narrative to use the same wires names that the instructions use:

• RED (R) wire to AIU ACC port "1"
• GREEN (G) wire to AIU ACC port "2"
• ACC port IN to transformer Hot
• BLACK wire to transformer Common.

Instead of the ITAD recognizing that the track is occupied, you'll instead need to activate the AIU to change the lights.

However, the signal bridge will work best if you use an ITAD or other sensing device instead of the AIU.

I wonder if part of confusion comes from being 2 "red" wires.  Barry's bulleted instructions shown below.  The "red" wire from ACC port IN to transformer is shown in pink to distinguish it from the "red" wire from the signal accessory.

Edit: I see Barry swapped red and green in a later post; the diagram has been revised to show this later hookup.  As he says, this swaps which signal aspect (vertical-proceed or horizontal-stop) turns on when you activate the accessory with the AIU. 

Hello Stan, Happy New Year to you.

This post could not have come a better time.

I bought a AIU at TCA Show in York this past fall and I am planning on hooking my signals up to the AIU tomorrow.

You get me straighten out on this topic before, this is just a bit of a refresher for me.

Thanks Again !!!!

Stan,

 I see Barry swapped red and green in later post. 

I swapped the wires because, when I read the instructions on MTH's web site, the RED wire was stated to go to the NO (normally open) contact of the ITAD. On the AIU, the NO contact is AIU ACC port terminal "1".

Still the same...

I am just going to buy ITADs for it, as this is the first time in 8 years I have used this AIU, and I seem to recall back then it had stopped working as well.

As Barry said, the ITADs are a better way to go anyway.

chipset,

I'm not sure why you would want to control what essentially is a block occupancy signal via handheld. The prototype told the approaching engineer that the track was either blocked or clear or that he could approach with caution (essentially).

If you want to use the bridge to indicate occupancy, here's a simple wiring diagram Dave Hikel gave me for wiring my two PRR Signal Bridges.  The diagram shows a different signal, but it works for the bridge.  The relay used is a Z-Stuff DZ-1008A.

Hope this helps,

George