Prior to deployment from a cable lay boat, the transponders are attached to the seismic cable at each ground station, typically every 50 metres. Once the bottom cable is laid, the acoustic system measures the ranges from the surface transceiver to the transponders to enable their exact positions to be established. This positioning process can either be conducted while laying the cable or later while shooting.

The transponders are small and lightweight and have been proven to be able to withstand the demanding and varied operational environment of OBC and TZ surveys.
Standard features include a depth rating of 500 metres, a unique acoustic ‘address’ enabling thousands of units to be laid in a single deployment and automatic battery voltage monitoring to allow users to better plan their maintenance schedules.

In OBC operations using a ‘squirter’ cable deployment system, ‘carapaces’ are available that provide a fast and secure means of attaching transponders to the cable. The carapaces are manufactured from tough plastic that encapsulates the transponder and optional RFID asset tracking tag, clamping it securely to the cable whilst protecting it from the high cable deployment and recovery speeds.
The carapace design which is now in use with many crews around the world has been proven to be easy to fit and reduces long term maintenance when compared with traditional tie-wrap and tape methods. The low profile shape of the carapace also reduces the risk of snagging and as it is acoustically ‘quieter’ in the water, creates less noise interference down the cable.

Technical Specifications

Features

• Versatile, low cost transponder
• Depth rated to 500 Metres
• Provides fast and efficient positioning of OBC cables
• Compact and rugged design
• HF frequency band from 35-55kHz
• Alkaline battery packs give up to 18 months listening life
• Optional RFID tags for asset tracking