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JT SONIC LISTENING EQUIPMENT

JT control console.

Use.-Submarines.

Contract number.-NXsr-65323.

Description.- Model JT equipment is an improved underwater directional listening system designed to supplant the Models JP-1, .2, and 3 equipment, with the following advantages :
1. Power training of the 5-foot line hydrophone.
2. Right-left training indication, giving bearing accuracy within + 1/2 degree. 3. Frequency range from 100 cycles to 60 kc. 4. Two-way communication between listening operator and conning tower. 5. Continuous target bearing indication at the torpedo data computer. 6. Continuous target bearing indication at the echo-ranging equipment, furnishing single ping reference.

Training system characteristics.-The d-c training motor is supplied by an amplidyne generator, which is controlled by a synchro-servo system, with an electron tube amplifier. Field current for the training motor is supplied from the ship's d-c line. A separate synchro system repeats the hydrophone bearing to remote repeaters at the control console, the torpedo data computer, and the echo ranging control station.
Connections to the hydrophone are made through slip rings, permitting continuous training in either direction.
The hydrophone is not retractable.

Power supply.-120 volts, single phase, 60 cycles, and 120 volts d. c.

Tube complement.-16 type 6SJ7, 2 type 6J5, 8 type 6SN7GT, 2 type 6SL7GT, 1 type 6AC7, 3 type 6G6G, 1 type VR15O, 1 type 5U4G, 2 type 6L6, 1 type 991, 1 type 25L6GT/G, 1 type 6E5, 1 type 6H6, 1 type 3-38, 2 type 3-50A.

Hydrophone.-The hydrophone is a straight horizontal 5-foot permanent-magnet magnetostrictive type made up of ten toroidally wound sections, the windings of which are designed to achieve side-lobe reduction.

Receiver specifications.-Signals received by the JT hydrophone are ordinarily fed to the JT amplifier, the output of which actuates the headphones, as well as the RLI meter, which indicates whether the signal was received from the right, left, or on the center line of the hydrophone. The right-left sense is obtained by separating the signals from the two halves of the hydrophone; a signal coming from right or left of the hydrophone normal axis will produce out of phase voltages in the two halves. The phase difference is used by the RLI system to produce a plus or minus d.c. to actuate the meter.
The audio amplifier accommodates signals over the range from 0.5 to 14 kc. Filters, selected by a panel switch, permit the lower frequencies to be excluded in three successive steps, a panel control adjusts the gain.
The JT installation also incorporates the existing JP amplifier, to be used as a stand-by and for special purposes. The JP amplifier may be connected directly to the hydrophone, or the signal may be passed through a supersonic converter, which converts signals in the 8 to 65 kc. range to audio frequencies, thus extending the listening range of the amplifier.

Intercommunication system.-The sonar talk-back amplifier is a separate unit, located near the control station, which permits two way voice communication between listening operator and conning tower and also permits the conning tower to listen to the signals being received. Additional units in the system consist of a conning tower speaker and a control unit containing switches and phone jacks.
The amplifier is a three-stage, cascade connected circuit, especially designed for low distortion. Its gain controls are set at installation to provide the correct sound level at the conning tower loud speaker.

JT system.

                    Dimensions and weights
     Unit         Navy Type No. Height  Width  Depth  Weight
                                Inches  Inches Inches Pounds
Master control unit  CRV-23460    38      20     17    233
Sonar talk-back am-  CRV-50200    21      17      8     32
 plifier.

Talk-back control    CRV-23461     6       3      5      5
 unit.
Talk-back speaker    CRV-49590     8       8      6     13
 unit.
Headset assembly     COF-49586     8       8     11      2
Motor-dynamo am-     CG-21-ACN    12      24     14    190
 plifier.
Converter amplifier  CRV-50199    18      20     14     51
 (in cabinet - JP
 amplifier not in
 cluded).
Hydrophone assembly. CRV-51075     7      65     11    135
 (a) Hydrophone      CQA-51074 (#1)2 1/2         60     26
 (b) Hydrophone      CRV-10365     4      65     10     63
   baffle.
 (c)Sound-absorbing  CRV-10366     3      10            63
   coupler.
Power-train mechanism:
 Mare Island         CRV-78241
 Portsmouth          CRV-78240
                     CG-211299
Bearing - repeater   CRV-24365     11      7      5      8
 switch.



(#1) Diameter.

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