RCA jacks and plugs (above) are common parts and should be available from just about any electronics store. The dual chassis RCA jacks are easily mounted into the layout fascia, while the phono plugs can be attached to throttles. The crews need to carry a switch key with them, and the easiest way is to attach one to the
monly-available RCA phono jacks and plugs as our own miniature version of a lock and key. They suggested mount- ing a pair of RCA jacks in the fascia in place of the usual push buttons. Each operator would then carry an RCA phone plug which acts as the key. The plug is inserted into the appropriate jack and the turnout is thrown. We designated the white color-coded
jack as the normal route of the turnout and the red color-coded jack as the re- verse route. Once the turnout is thrown, the key must removed from the plug if there is more than one lock location for that turnout. Otherwise, it will not move if someone tries to throw it from the other location, such as the other side of the module. This has worked so well for us that we have at- tached RCA “keys” to our Digitrax throttles. I even carry an “RCA key” on my key chain.
The circuit used for this is fairly sim- Wiring diagram
The circuit is pretty simple and straight forward. The resistors are present to slow down the motion of the throwbar to a more prototypical speed.
Digitrax throttles with nylon cable ties (below). They can also be at- tached to key rings or just carried in one’s pocket. In order to be- come “keys,” the phono plugs must have their internal connections bridged. The plug on the right has been modified for use as a key by soldering a wire between its two contacts (above right).
ple and is shown in the diagram below. However, I have only used this method of control on Tortoise machines and don’t know whether it will or won’t work with other types of switch ma- chines. Basically, it works by providing current to pins 1 and 8 of the Tortoise. Plugging a modified phono plug (the plugs are modified by bridging their in- ternal connections) into one of the jacks completes the circuit. The Tortoise switch machine is only powered when the key is inserted into a jack, holding the points in position even if it’s not under power. The advan- tage is that a large power supply is not needed to power a whole layout. In fact, we use a small plug-in wall trans- former rated at nine volts and 300 mil- liamps as usually only one or two Tor- toises are activated at any given time. You may have noticed the two resis- tors in the circuit. Technically, they are not needed at all and the circuit will
work fine without them. However, they are included if you want to slow down the throw of the turnout for a more pro- totypical appearance. We are using ½- watt 2.2K ohm resistors based on our power supply and we thought the motion looked good. You may have to vary the value of the resistors up or down slightly depending on how fast or slow you want the throw bar to move. I obtained my RCA jacks and plugs from TriState Elec- tronics. They are local to me but also have a web site at www.
tselectronic.com. We use the dual chassis RCA jacks, part number 30-537. The RCA plugs are part No. 30-534.
Mounting the RCA jacks in the fas- cia will mainly depend on the way your fascia is constructed. Typical modules that have a 1″×4″ lumber frame and tempered hardboard fascia will need to have a spot routed out in order to in- sert the RCA jacks. Use a router to pro- duce a 2″ long׳₄″ wide depression
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