The special purpose electrical cable is pretensioned on the hydraulic reeling machine (Figure 1-12-8). The cable contains 30 shielded conductors encased in a braided steel strength member, and is protected by a waterproof, insulated, outer covering of polyurethane. The cable assembly and reel is bolted to the hydraulic cable reeling machine and is connected electrically by a cable connector that is connected to the reeling machine slip ring assembly. The outboard end of the cable is provided with a strain relief connector that provides mechanical and electrical connections to the sonar hydrophone.

The special purpose electrical cable is normally 520 feet in length, but may be shortened to a minimum of 490 feet to compensate for cable unserviceabilities and salvage. This minimum length ensures that 465 feet of cable is available for payout (490 feet less four turns on the cable drum and the amount of cable required to thread the reeling machine, totaling approximately 25 feet). Thus, the maximum transducer depth available when using a 490 foot cable is 425 feet (465 feet of usable cable less the helicopter hover altitude of 40 feet). The lowering sequence should be stopped before the lower limit switch on the reeling machine is actuated. Use of the lower limit switch to stop the transducer lowering sequence will reduce the reliability of the protective devices.