dumb waiter service. The design arrived at was not standard; it was the 300 foot tower, The mechanism for operating the safety grips was completely developed by H & N and called for specially designed safety grips similar in general design to those used for the skip hoist on entirely different from that of the 300 foot towers, It worked only in the event of a broken rope or slack hoisting rope conditions, as no personnel were to be carried on the dumb waiter. The hoisting rigging for the dumb waiter was mounted entirely be- low the level of the tower house floor to eliminate any obstruction at the unloading space at the top, The cable was attached low on the dumb waiter platform subframing to permit the platform to go 2 feet above the floor level, for easier handling of freight in loading or unloading. Extra-flexible hoisting cable was used for hoisting the platform; this allowed the use of comparatively small diameter sheaves. All sheaves were cast steel with grooved bronze bushings and were provided with Alemite lubrication fittings. The hoisting rope operated inside of the tower line. A pipe guide was provided for the hoisting rope at a point where the rope operated between the stairs and the tower framing. This was done to eliminate the possibility of the rope rubbing against the tower or stairs, Figure 5.11-10 shows assembly of a dumb waiter for a 75 foot tower, On September 19, 1950, H & N received a request from Edgerton, Germeshausen & Grier, Inc. asking that motor operated roll-up type doors be provided on two sides of the 75 foot tower house. These doors and operating motors were to be mounted on the outside of the building, to close openings 14 feet, 3 inches wide by approximately 7 feet high. This request was approved by J-Division on September 20, 1950, and the H & N Mechanical Engineering Department contacted the Los Angeles representative of the Kinnear Mamfacturing Co., at the request of EG&G, to obtain information on the type of motor operated rolling doors required. On the basis of the information obtained about price and delivery, the doors were purchased from the vendor by H & N. The vendor furnished shop drawings of the doors, which were approved by the Mechanical Engineering Department. Since the doors would have to be installed in the field, it was necessary for H & N to prepare installation drawings for the doors. This work was shown on two drawings which supplemented the vendor's drawings and showed how the door guides were to be attached to the tower cab. Because the door and motor were mounted outside the building and above the roof, it was also necessary to design a support for them. As this was a special condition, such supports were not supplied by the door vendor, These drawings were completed October 5, 1950, am prints of each were submitted to the vendor for his check. They were found to satisfy the conditions required for mounting the doors, and the doors were installed according to the drawings. The electrical facilities for each of the six 75 foot towers consisted of lighting panel, lighting fixtures and wiring, time-switch- 5151