The active mode is an echo ranging mode wherein the sonar produces 3.5 or 35 millisecond acoustic pulses that are radiated through the water from the projector part of the transducer. The power output is 500 or 5000 watts. Returning target echoes are received by the hydrophone and processed into a left and right half-beam for each sector.

Target bearing is determined by the phase difference existing in the left and right half-beams formed for each sector scanned. Bearing of the target is resolved from the centre of each of the eight 45 degree sectors: a greater phase difference of the two signals results in a proportional displacement of the echo off centre from the centre of the sector. Target range is determined by the elapsed time between transmission of a given pulse and the return of a target echo. Bearing and range are presented simultaneously as a single target pip on the Plan Position Indicator (PPI).

Variations of the speed of sound in water due to temperature of the water surrounding the transducer are compensated for automatically. An audio signal is developed for each returning target echo. A different nonharmonic tone is generated for each of the four sectors in each Cathode Ray Tube (CRT) half. When the AUDIO switch on the receiver is set to ALL, these audio signals are applied to the aircraft intercommunication system in such a manner that signals representing the left four sectors of the PPI (7, 8, 1 and 2) are mixed with the signals for the right four sectors (3, 4, 5 and 6) and applied directly to the operator’s head-set. When the audio switch is set to ONE the audio from the sector in which the cursor is positioned, is applied to both earphones.

With the ICS set to SONAR DIRECT, a different nonharmonic tone for each sector of left or right bearing is applied directly to the operator’s headset, with the tones of the left half of the CRT applied to the left earphone and the tones of the right half of the CRT being applied to the right earphone. The nature of the object causing the echo can be determined by the outline and intensity of the target display on the PPI as well as the quality and intensity of the audio. The opening or closing speed of the target within the cursor circle is displayed automatically on the RANGE RATE-KNOTS meter. Stationary objects, reverberations and clutter obscuring moving targets on the CRT are eliminated by use of the MTI THRESHOLD switch. This switch causes objects moving slower than 1, 2 or 3 knots when in the LOW, MED or HIGH positions, respectively, to be blanked.