Sea Marshall® Crewguard CG-121 MKII is ideal for monitoring large areas such as Jetties, Oil & Gas platforms, Wind farms, Fish farms, Harbours, Marinas also ships from small single handed fishing vessels to super tankers. A high-gain external antenna can be added to the Crewguard to increase its effective range making it ideal for monitoring very large areas. The Crewguard can also be linked to an external auto dialler to provide automatic ?SOS? coverage of unmanned areas.