Coax Systems:

Typically, RSL coax systems consist of one or more of the Multi-Channel Series (MCS) of telemetry MODEMs and also includes one uplink real-time video channel.   These channels are them summed onto the high-voltage system power.  A uProcessor in the underwater instrument scans various sensors, formats the data, and telemeters the data to the surface processor rack.  The surface rack transfers the data into the surface PC and displays system parameters, as well as selected sensor data on the GUI(Graphical User Interface).   Camera lights and other switch functions are controlled by either the GUI or by surface rack mounted switches.

Typical sensors in underwater Data Acquisition Systems include; CTD (conductivity, temperature, depth ), Ph Sensor, 02  Sensor, Acoustic Velocity, Altimeter, Turbidity, ADCP, and more.

See the spec sheet for the Multiplexer; Multi-Channel Series below.

Fiber Optic Systems:

These systems may contain the same uProcessor card and function as the coax series to control external sensors or digital I/O as well as the period sampling of oceanographic sensors.   RSL's most commonly used uProcessors are in the PC104 format with daughter cards that stack onto the main mother cards.   These cards can be Digital I/O expansion units, as well as additional serial data cards for the RS-232/422/485 older type sensors.

The RSL fiber optic transceiver also has the capability to also handle all the sensor communications on an individual sensor basis without needing the uProcessor card.   The main motherboard, the Fiber Optic Module, contains four uplink video channels, plus four RS-232 channels and two RS-422 channels.  Expansion cards stack onto the main unit and includes these optional daughter cards; 

  • Gigabit Ethernet 4 Port Switch
  • HD-SDI Camera Interface
  • 16 Port Isolated RS-232
  • 8 Port RS-422/485

Two fibers or more may be necessary for multiple high rate uplink data channels, especially for several real-time HD cameras and 1000 BaseT Ethernet communications.

Separate expansion units, such as USB to  4 or 8 port RS232, or an Ethernet expansion series card are also available.

Ethernet Cable Systems:

A few underwater communications and power cables incorporate 'flat cable' style Ethernet conductors.  A proprietary Long Line Booster system can provide reliable video and communications over 3000ft of this cable. Lower total data rates, as compared to fiber systems, along with two video cameras are supported on this series of multiplexers.

Acoustic Transmitters/Receivers:

Acoustic Receivers: 

Many systems have been designed and shipped for the deep ocean environment.   Typically 6 inch pressure housings are used and the corresponding circuit cards have a rounded shape with the I/O connector on the bottom side ( see photo - Acoustic Transceiver Module).  

Other board formats are also used ( see photo - Acoustic Receiver) and are per customer requirements.

  • Very Low Noise
  • Analog or Digital TVG (Time Varying Gain)
  • Transducer Impedance Matched Input
  • T/R Networks
  • TVG Control Generator Cards 

Acoustic Transmitters:

  • Analog Sine Wave Amplifier (Up to 400w)
  • Digital Contolled Pwr Amp ( Up to 3000w)
  • Storage Cap/Cap Charger Cards

Spec Sheet:

Multi-Channel Series         RSL7301                 

The RSL multiplexer series has 
added capability over other systems currently available.  The MCS series not only provides video and telemetry but adds a uProcessor control system  in the subsurface unit.   This added feature  allows for the subsurface unit to communicate with multiple oceanographic sensors and systems, format the data, and sends the data to the surface for display on the GUI (graphical user interface) and stores the data in memory on the host computer. .

RSL 7230 Surface Rack:  This system has two unassigned Bi-Directional telemetry channels and one uplink color video channel.  The two telemetry channels operate at  38.4K and 115K baud rates.  The GUI (graphical user interface ) software is included with this unit.  A dedicated 19.2K baud link provides for the uProcessor communications for digital I/O control, such as light on/off functions, camera control, and data querying of oceanographic sensors.  Within the surface rack, the RSL 7200 series, is an internal 375volt power system for the towfish electronics unit.  The rack  and is housed in a standard 3U, 19" enclosure.    

The video channel is shared with the 115K baud sonar telemetry link and is controlled by the GUI to select either avoidance/search sonar mode or transfer to the inspection mode enabling the color camera system.  An optional 
camera  switch circuit card can be added  so that a second camera can be selected to  be viewed.                        

Standard bus voltages of 48, 28, and 12Vdc are available in the
tow fish electronics for powering the cameras, LED lights and customer provided external sensors ( depth, sonar, CTD, etc.).  Power switching is via GUI selection and controlled by a six channel solid state switch circuit card in the subsurface electronics. 

Subsurface electronics are supplied with the assembled rack and power system only.  Two standard optional housings are available for 2000m and 6000m depths, 


  • uProcessor control in the subsurface unit for multiple sensor additions
  • Graphical User Interface Control
  • Software Upgradeable for future sensor additions ( pH, O2, Turbidity, CTD, Compass, Attitude, etc.)
  • Field Proven Telemetry System
  • Optional 9600 Baud Channel
  • Optional Internal Compass, Attitude System (adds approx. 5" to rack length) 
1 v p-p, 75 ohm, Rack Unit BNC.

Digital Data, Unassigned
Chan 1:
RS-422/485, 115K Baud, Full Duplex, 4-Wire(time shared w/the Video Channel)
Chan 2:
RS-232, 38.4K Baud, DB-9
Chan 3:
RS-232, 9600 Baud, DB-9 (Future Option)

Digital Data, uProcessor Controlled, Packetized
up to 1600 bytes per second, packetized
RS-232,   4 Channels
RS-422/485,   3 Channels, Full Duplex, 4-Wire
Host computer I/O capability dependent, up to 1600 bytes per second
Optional;  4 Analog Channel Outputs
                 4 Analog Channel Inputs

System Rack Power
Supply Voltage: 
120 VAC, 240VAC (optional)
600W w/ subsurface at full capacity

19" Rack mount, 3U height
6" OD, length approx  28" (Rack Only, Housing Optional)
Operating Temperature, 
   Surface; 15 to 40 deg C, 
   Subsurface; 0  to 40DegC

Subsurface Electrical
375Vdc Input Bus
48Vdc/125W max
28Vdc / 125W max, (24Vdc optional)   
12Vdc / 125W max

Tow Cable
Coax, 50 ohm, 4000m of RG213 or equivalent
Combined Data and Power onto a single coax


Electronic Design and Manufacture


Power/MUX Interface

FDM Multiplexor

Specifications subject to change without notice

Acoustic Receiver w/Analog
20,30,40dB logR TVG Controller

HV Power/MUX Interface

Acoustic Transceiver

Typical User GUI

Video Modulator

Surface Controller