Item used to switch the power for the red tail lights circuit from the trolley pole to the battery circuit when the trolley pole was being reversed and not able to provide power to the internal and external lights. Made by the SECV. Salvaged from tram 14 during the project to renew the wiring and electrical arrangements of the tram. The box was located adjacent to the driver's windows and would click when the trolley pole was placed back on the overhead.Demonstrates an item fitted to a tramcar to switch an external battery tail lighting circuit.Wooden box made from softwood with bevelled corners, plywood top painted green containing an 8 Ohm "Post Office" type relay (see reference) fitted with two "break" contacts and associated insulated wiring soldered to the relevant contacts. See item 9024 for an associated drawing. Two examples held.fuse, tram 14, tramcars, tramcar maintenance, electrical switching