system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does a trolley bus keep its poles on the correct wires on large intersections or when one set of wires splits into two that go in different directions?
gpt
There are no universal answer to this as each trolley system is different. Most of them do have a type of switch known as a "frog" which are switched by an electromagnet somehow triggered by the driver. One way to trigger these is by connecting the electromagnet in line with the lines so that a current draw will flip the switch. The driver can thes select the possition of the frogs by pressing the accelerator as he goes through the junction or coasting. Other types will have contacts on the side of the wire detecting the precense of a bus. These contacts will only be triggered if the bus is in the lane next to the wires as the poles will have to go sideways to the overheads. Others just use radio signals connected to the bus indicator lights so when the driver indicates he also switches the frogs in the right direction.