Abstract: Walk through test system for testing devices such as pull stations, smoke detectors, alarm bells and the like for alarm and trouble conditions without the assistance of a central panel operator. The devices are connected in a loop or loops distributed throughout one or more zones remote from a central panel. Alarm and trouble conditions are detected at the central panel. When a device is placed in alarm by the workman, a coded alarm is sounded which is aurally detectable by the workman at the location of the device, remote from the central panel. The coded alarm identifies the zone loop in which the device is connected. When a trouble condition is created in a loop by the workman, an alarm is sounded which is aurally detectable at the location of the loop, remote from the central panel. The alarm is coded to indicate to the workman that a trouble condition has been detected at the central panel.

Abstract: A driverless vehicle is provided with support wheels on one side and drive wheels on the opposite side. The drive wheels perform the dual function of supporting one side of the body and propelling the vehicle by frictional contact with a drive shaft. The drive wheels are coupled together for oscillation about a vertical axis and are biased to a drive position. The vehicle body is provided with a cam for causing accumulation upon contact with another vehicle.

Abstract: An annular seal of resilient material is disclosed and having an axially directed groove containing a spring between two interconnected body portions. At least one of said body portions has a sealing lip projecting in a radial direction generally opposite the location of said spring. Said groove has portions spaced from the bottom and in embracing contact with opposite surfaces of said spring. Said groove bottom being a portion of an ellipse and having embracing contact with a juxtaposed portion of said spring only when the sealing lip is under a compressive load.