This thesis presents the design of an Electric Fence Monitoring System (EFMS) which detects and announciates fence malfunctions indicating operational ineffectiveness. The EFMS consists of a master unit and up to sixteen slave units. Each slave unit monitors a single remote point on the fence. Slave units gain their power from the electric fence pulse itself. They use a unique transmission algorithm to transmit the peak electric fence voltage, to the master unit. The electric fence wire is used to convey this transmission. The master unit uses a non-linear switched capacitor filter with variable gain control, to detect the slave unit transmissions. This unit displays the peak voltage at each monitored point and allows the setting of alarm trigger points. This thesis includes modelling of the electric fence energiser and typical electric fence line, and the detailed design of the two units that makeup the EFMS.