Edgetech 4125I User Hardware Manual page 21

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adapter cable for power and communication also connects to this end cap. The cable snakes through a
hole in the transducer array section and includes an inline connector for connecting to the tow cable. The
towfish interfaces with the topside over a 10BaseT connection that uses VDSL modems in both the towfish
and the topside processor.
The 4125i towfish is shipped with a choice of dual side scan sonar subsystems with two frequency
configurations, 400/900 kHz or 600/1600 kHz. The 400/900 kHz option is the best choice for general
survey work providing good range and resolution. The 600/1600 kHz option is best for detailed object
identification as it provides high resolution. An optional hull scanning kit is available to support the angles
necessary for detailed hull scans.
The side scan sonar subsystems are frequency-modulated (FM), dual-frequency, that uses EdgeTech's
proprietary Full Spectrum "Chirp" technology to generate high-resolution, side scan imagery at longer
ranges than conventional continuous-wave (CW) systems. The frequencies are transmitted as linearly-
swept, wide-band, high energy acoustic pulses, and the received echoes are processed into high signal-
to-noise (SNR) images that are displayed and recorded by EdgeTech's Discover 4125 software.
There are two towfish configuration options available for the 4125i depending on the desired survey
depth. The standard towfish and tow cable provides for survey operations down to 50-meter water depth
and operates on an Ethernet tow cable up to 150 meters in length. The "telemetry" version has a towfish
and topside modem configuration that supports tow cables up to 600 meters that allows the system to
operate at greater depths. A Depressor Wing and Keel Weight option is available to assist with deeper
water operations.
The towfish is equipped with a stainless steel nose for hydrodynamic balance and two convenient carrying
handles. A towing arm is rigidly mounted to a tow point on the top of the towfish housing adjacent to the
tow cable connector. The tow cable attaches to a shackle on the towing arm.
Additional mounting holes are provided on the tow point should it be necessary to reposition the towing
arm forward or aft to adjust the balance of the towfish. The towing arm also includes a safety release
mechanism, which causes a shear pin to release the tow point should the towfish hit an obstruction or
become snagged. If this happens, the towfish will rotate nose down, and a safety cable, which is attached
from the tow point to the rear of the towfish, will pull the towfish over the obstruction or through the
snag, stern first.
4125i/4125 SIDE SCAN SONAR SYSTEM 0004823_REV_G