To protect it against the artillery, mortar, and rocket attacks, all communication equipment was either underground or heavily sandbagged. Major Shepherd moved his communications center into a shelter which was made from 4 conex boxes, 16 feet underground.[64] This nerve center housed the teletype equipment and switchboards which provided service for 65 on-base subscribers and 40 external radio relay voice circuits. In spite of the protective measures, the antenna and internal wire system sustained damage on a daily basis. Following every barrage, wiremen tracked down cuts and spliced them and repaired damaged antennae so that the various nets were back in operation within minutes. The maintenance and repair of the electronic devices used for perimeter security placed an additional burden on the communicators.(173) While trucks and forklifts were not exactly delicate equipment, the base motor transport personnel had their share of problems. These vehicles were used constantly. During the summer and fall of 1967, they were used to haul rock for the repair of the runway. Throughout the siege, the drivers carried ammunition from the berms to the distribution points and supplies from the drop zone to the combat base. Many of the trucks were in bad shape and mechanics worked around the clock to keep them rolling. The biggest headache was caused by flat tires, of which the constant shelling produced an abundance; the drivers became paste and patch experts of the highest order. More often than not, these men were caught out in the open when the enemy decided to pound the base. Since their cargo usually contained high explosives, the drivers had good reason to be apprehensive. Some simply bailed out of the cabs during the attacks and dived for cover; others, performing a wild imitation of the Grand Prix, raced for revetments. Needless to say, the base speed limit of five miles per hour was frequently violated.(174)