hose, and diver communications cable, which usually also serves as a lifeline strength member. The pneumo hose is open at the diver's end and the other end is connected to a pressure gauge on the surface gas panel, where the supervisor can use it to measure the diver's depth in the water at any time. This is done by measuring pressure of the air in the pneumo hose after a thin stream of bubbles has been emitted from the open end which ensures that the hose has been purged of water so that the internal gas pressure is effectively constant and equal to the ambient pressure at the open end. The umbilical serves as a lifeline and must be capable of lifting the diver out of the water safely. Maximum permitted service life for rubber breathing air hoses is 12 years, but synthetic (unfilled polyurethane elastomer) lined hoses may be used without time limit while in good condition as long as they pass inspection and testing. Hot water supply hoses are more likely to be rubber lined, and polyurethane external sheathing is common for all umbilical hoses and cables. A typical 4-part diver umbilical will also have a bore hot water supply hose for the diver's exposure suit. A 5-part diver umbilical will also include a video cable to allow the surface controller to see the video picture transmitted to the surface from the diver's hat camera (video camera mounted on the helmet, facing forward, with a field of vision similar to that of the diver). An excursion umbilical from a wet bell would be similar in construction, but shorter than an umbilical supplied directly from the surface for similar work. For saturation diving from a closed bell, a typical diver excursion umbilical may be an 8-part umbilical with a breathing gas supply hose, gas reclaim hose, hot water hose, pneumo hose, tracking hose, communications and lifeline cable, video cable and hat light power cable. Early diver umbilicals were simply the individual components bundled together and taped every metre or so with duct tape. These bundles tend to distort and produce kinks in the components caused by bending (particularly dangerous if the kink is in the divers gas supply hose), and require frequent maintenance. More recent umbilicals usually comprise all the components laid together like a twisted rope, so that there is little chance of a kink, no separate lifeline