Some versions had a partition between the driver and the passengers. These partitions often had a small slide-back glass window, or were completely made of glass with a manual or electric winding system. The passengers could speak to the driver through a communications tube, or, from the 1920s, through an electrical device similar to a telephone. Some designs included a switch panel in the rear passenger compartment, which contained a speedometer and switches to impart the most common instructions to the driver via a lighted dashboard panel, such as "stop", "left", "right", or "home".