One of the more important developments in railroad technology was the switch.  Called a turnout by civil engineers, the track switch allowed trains to go to two different places instead of just one.  For model railroaders, an equally important development was of the switch machine, which used two solenoids and a pair of push buttons to operate the switch.  In this way, a person standing on one side of the train layout could operate a switch on the far side of the layout without moving anything more than a finger.  Model railroaders often use the civil engineering term “turnout” to avoid any confusion with the term “switch” of the electrical variety.  Out on the real railroad, however, using the term turnout is a sure guarantee of derision from railroad personnel.

     Arnold rapido had remote switches which had an ingenious mechanism.

     Inside the switch machine are two coils of wire.  When electricity is passed through one of these coils, magnetic inductance is created.  The switch machine has a slug of steel inside which is connected by a mechanism to the switch points, the two moveable rails which guide the trains to one side of the other.  Activating the coil of the switch machine causes the points to move to the opposite position.

     The Arnold rapido switch machines had an unusual feature, one not commonly found on model railroads.  If electricity continued to flow in the activated switch machine coil, heat would build up and eventually the coil would burn out.  The Arnold switch machine had a pair of electrical contacts which prevented this.  Once the switch machine had done what it was directed to, the coil itself was disconnected electrically, but electrical current would continue to flow.  In this way, Arnold rapido switches could send electrical current to other devices, effectively providing position indication to another location.  Here are two examples:

     Here, the 0722 Switch Control button is used.  The 0722 had internal light bulbs which visually indicated the track switch’s position.  Earlier, Arnold had marketed the unlit 0721.

0722 Switch Control

     In another application, the 0760 Color Light Signal has been added, another way to indicate switch position.

     The Arnold rapido switches also had another feature; they were current routing. In this way, track power was only fed to the track for which the track switch was aligned.

     Using the current routing feature of the track switch allowed control of multiple locomotives, with control achieved by simply changing the position of the track switch.  There were several examples posted in the Arnold technical books.

     Here, a locomotive is controlled by the position of the track switch.

     This drawing shows a more complicated situation.  At this passing siding, one train could enter the station and then be stopped. After changing the direction switch on the transformer, a track switch could be opened and a second train then operated in the opposite direction.