Abstract: The mast has a housing arranged to be mounted on the roof of a vehicle such as an emergency vehicle at the usual location of a vehicle light bar, whether or not a light bar is associated with the mast housing. A seal unit is located at the lower end of each telescoping mast section engaging the next outer mast section. The seal unit leaves the lower end of all mast sections unobstructed so that a tubular passage is formed from end to end of the mast. A retractable power supply cable is located in the passage of supply power to the electrical appliance mounted on the top of the mast. There are electrical plug connectors at each end of the mast for releasable connection with the electrical fixture at the top and with the vehicle power supply at the bottom of the mast. The mast is mounted on an offset pivot which simplifies the pneumatic-actuating system which tilts and telescopes the mast, and also enables the mast to tilt by gravity from telescoped retracted vertical to stored horizontal position.