Tecmarine can supply Navitron, Simrad TMQ autopilots.
Autopilots or electronic self-steering is controlled by electronics utilising one or more input sensors, invariably at least a compass, gyro, GPS, fluxgate etc, and sometimes wind direction or GPS position versus a chosen waypoint. The electronics module calculates the required steering movement and a drive mechanism (electrical or hydraulic in larger systems) causes the rudder to move accordingly.
There are several possibilities for the interface between the drive mechanism and the conventional steering system usually dependent upon vessel size/weight.
Most common systems are:
Hydraulic, in which the electronics are connected to existing hydraulic controls via solenoid valves. This is the least intrusive method of installation.
Direct drive, in which an actuator is attached to the steering quadrant, at the top of the rudder stock inside the boat.
Wheel mounting, in which a motor is mounted near the steering wheel, and can be engaged with it when in use. This typically involves either a belt drive or a toothed gear-ring attached to the wheel itself, and is a common option for retro-fitted installations on yachts with a wheel.
Tiller-pilots are usually the only option on smaller vessels steered with a tiller. They consist of an electrically driven ram which is mounted between the tiller and a fitting on the side of the cockpit. Some are entirely self-contained, needing only a power supply, while others have a separate control unit.