For those not familiar with these horrible weapons this is a contact mine, within those horns are the components of a lead-acid battery with the acid contained in a small glass tube. If a ship hit the mine one of the horns would be distorted breaking the glass tube and so completing the battery, the voltage from this battery would then fire an electrical detonator and so explode the mine.
These are as evil as land mines, and as non discriminatory sinking friend or foe unlucky enough to meet them.
If you ever see a photo of a mine-layer, you will notice that each mine is on its own little rail-car set on the rail-road-like tracks running down the mine-layers deck. This little rail-car is in fact the mines anchor, built into this is a drum of wire adjusted to a pre-set length, varying with the location of the mine-laying operation. Once dropped off the stern of the usually very fast moving mine-layer, it would sink to the sea bed and after a preset time the drum would be released and the mine would travel towards the surface, to come to a stop, about 6-10 ft below the surface, where it would sit till someone hit it, or it got swept by mine sweepers.
BTW the mechanism used by the RN to control the time on drum release was of the highest technical design. A sugar lump was placed in the brake drum . when the sugar lump dissolved, the drum brake was released and the mine was in business.