Unfortunately, none of the photos I reviewed, did a good job of explaining a tongue and mate switch. Several were shown, and if you see a black box next to the rail where the tongue ( switch point) swivels in a controlled arc, that is the switch point. To move the switch point to a difference route, one had to open the box and there was a spring inside that could move and the spring held the point in the desired position. After the route taken was not needed, the switch had to be re-thrown to allow traffic to use the usual route.
When this type is used in electrified trackage (overhead electric wires) , the switch box was set up for an electrical movement by use of the controller in the track vehicle to change the switch movement without having the employee manually opening the box. When the operator ( engineer ) came to a certain point on the track, the electrical trolley pole would send a charge to the switch if the operator wanted to use the diverging route: If the controller was off, the switch stayed in the position ir was in; if the operator wanted to diverge, the operator would allow some current to be sent to the switch and the point would change. In some cases in trolley use, the operator could lean out the front window and use a long rod to open the box and move the spring throw. There are both single and double tongue switches in use today in both freight and transit.
There were thousands of electrical tongue and mates used in the trolley days, and also on docks with electrical overhead where this type of switch was used. I have had an electrical engineer tell me that the tongue and mate switch would not work after I explained what type of switch I would be using on an installation of a trolley line. I don't think I ever got him to realize the many years that had past and they were still working today.,
