The Sound Room is located in a bottom compartment well forward in the ship in order to minimize noise generated by the ship’s own propeller. The cross-sectional and cut-away views of a typical ship below, show the dome and projector lowered into working position, extending about 45 inches below the bottom of the keel, and the dome is about 3 inches below the keel when retracted into the” housed” position. The units mounted in the Sound Room are as follows:

            Navy Type No.                Unit No.                    Name of Unit
            CCU or CMT-
            78229 or 78230                   5                    Retracting Gear
            CAO-21 1109                      7                    Magnetic Controller
            CAO-24176                       12                    Push Button Switch (3 button)
            CW-78207                         25                    Projector

RETRACTING GEAR
The other unit of the sonar equipment that is not located in the Sound Hut console is the retracting gear, which is in the hull of the ship near the keel. This retracting gear is similar to that of the QGB equipment. However, it is slightly smaller because the QJB transducer is smaller. The Bell System retracting gear, had large pillars of malleable iron, and weighed about two tons.

TRANSDUCER
The transducer is made up of ADP crystals (Ammonium dihydrogen phosphate crystal, referred to as ADP. ADP crystals can be used both for emitting sound and receiving sound and have very good sensitivity.) mounted on a steel plate. These crystals project perpendicularly from it a distance equal to one-quarter wavelength of sound in the crystal medium. Opposite the crystals on the reverse side of the mounting plate are steel rods extending a distance equal to one-quarter wavelength of sound in the steel medium. These steel rods are longer than the crystal units because the velocity of sound is greater in steel than in crystal. This system of mounting the crystals with the resonating rods results in greater power output than if the crystals were used alone. It has the disadvantage of making the transducer frequency sensitive. The crystal array is housed inside a rubber sound window. The space inside the sound window that is not occupied by crystals is filled with castor oil that has been treated to remove all air and moisture. This castor oil protects the crystals from damage by moisture, because it excludes water.

DOME
the retracted position, the dome protruded three inches below the keel and was 45 inches (3 ¾ feet) below the keel when extended. A two horsepower motor was required to raise and lower the dome with a provision to do it manually. A set of indicator lamps in the Sonar office indicated the position of the dome -- red was for the working position, green was for housed and red/green for any intermediate state. In the housed position, the dome, the raft, and the oscillator were drawn up to the top of the trunk. The top of the raft butted up against a seating ring under the top of the trunk, thus making a watertight joint. This allowed the portable cover to be unbolted, in the event that either of the oscillators had to be changed. The procedure would only work if the dome was undamaged.

The Staybrite window of the dome, was aligned with the face of the oscillator so sound waves could be transmitted and received in a 360 degree arc in 5 degree steps. Staybrite was secured over a ribbed section of heavy cast metal and this ribbing is what produced the window effect.

Maximum design speed for the dome was 25 knots. When retracting or extending the dome, it was necessary to check the voltage of the mains supply. In a 220 volt mains' system, the voltage could not drop below 180 volts. If it did, the contactor in the control board could fail to operate thus causing the dome to bump against the end stops and cause damage.

The dome was normally housed for any of the following conditions: when working cables; when working bottom lines; when entering or leaving harbor; when steaming into a heavy sea; if cessation of Sonar operations could be tolerated; and finally, when navigating in shoal water and Sonar is not required for navigation.

Lowering Dome with Retracting Gear

            (a) Close motor line switch if it is open.

            (b)  Momentarily push the DOME DOWN button in console or LOWER button in Sonar Room. The hoist motor should start and the DOME DOWN-PART lamp in the console should light. In an emergency, the dome may be stopped by pushing the STOP button in Sonar Room, or by opening the motor line switch.

            (c)  As soon as the hoist motor stops, open the motor line switch. Remove the cover over the end of the worm shaft. Remove the hand crank from its clip fastening, slip it on the end of the shaft and crank the dome down tight to its full seated position (about 42 revolutions, indicated by resistance to the crank turning). The DOME DOWN-FULL lamp in the console should light. The dome position indicated on the limit switch box may be used as a guide. Remove the crank from the shaft and replace it in its clips. Replace the cover over the end of the shaft. Close the motor line switch.

            (d)  It is important that training be avoided until the raft of the retracting gear has been fully seated.

Raise Dome with Retracting Gear (If necessary).

For hand-seated projector equipments, observe cautions for hoist motor, coupling shaft and hand crank. Momentarily, push the DOME-up button on console or the HOIST button in Sonar Room. Dome may be stopped in any part of the travel by pushing the STOP button in Sonar Room or by opening motor line switch. Observe that DOME DOWN-PART red light comes on, and that after a short interval the DOME DOWN-FULL green light goes out. Observe that D0ME DOWN-PART red light goes out when dome is fully retracted with power seated equipments. In case of hoist-motor power failure, it will be necessary to crank the dome up by hand using the procedure for hand-seated equipment. With hand-seated equipments, the hoist motor will stop when the dome is almost fully hoisted. If seating of the raft against the gasket in the trunk is required, after the motor has stopped:

            (a) Open motor line switch.

            (b) Remove rover over end of worm shaft.

            (c) Remove hand crank from its clip fastening and slip it on the end of the shaft and crank the dome up tight, until the crank will turn no more (about 42 revolutions). The dome position indicator on the limit switch may be used as a guide. In case of hoist-motor power failure, it will be necessary to hand crank the dome into position.

            (d) Remove hand crank and replace in clip fastening. Replace cover over end of shaft.

            (e) Close motor line switch.

            (f) Observe that DOME DOWN-PART red light is extinguished.