This is what the controller would have looked like on tram 23. The handle on the left which was used to control the tram was an English Electric Dick Kerr type DB1K33E.
In 1917 Dick, Kerr & Co., a partnership of Glaswegian merchants W. B. Dick and John Kerr, acquired the United Electric Car Company, a trams manufacturer of Preston, Lancashire. In 1918, The English Electric Company, Limited (EE) was formed. In 1918 EE took over Dick, Kerr & Co.
The handle on the right is the Westinghouse air brake.