Master-slave compass system - uses stepping motor and digital circuit to bring in alternative magnetic master in case of failure

摘要

A multi-compass system has a master compass and one or more slave compasses so arranged that if the master compass fails the slave(s) can be switched to operate from another magnetic master compass. The needle from the store is controlled by a stepping motor. A control circuit connects this stator winding to the master compass needle. A four quadrant multiplier is provided so that the step signal approximates to a sine wave which is used as a motor reference and excitation signal for the store motor. The stepping arrangement is digital and the number of connections are fixed for each degree of master compass needle movement.