a fixed center pivot structure including a vertically extending water supply pipe having upper and lower ends;

a swivel structure rotatably mounted on said upper end of said water supply pipe and being in fluid communication therewith;

a center pivot span structure secured to said swivel structure and extending outwardly therefrom;

said center pivot span structure including a water delivery pipe supported upon one or more self-propelled drive units;

a control panel mounted on said center pivot structure and which has a plurality of electrical and/or signal wires extending therefrom;

an elongated, vertically disposed, hollow mounting tube, having upper and lower ends, fixed to said center pivot structure and which extends upwardly from said swivel structure;

said swivel structure and said center pivot span structure being rotatable with respect to said hollow mounting tube;

a collector ring enclosure, having upper and lower ends, rotatably mounted on said mounting tube above said swivel structure;

said upper end of said mounting tube being disposed adjacent said upper end of said enclosure;

said collector ring enclosure being connected to said span structure whereby rotation of said span structure relative to said center pivot structure causes said collector ring enclosure to rotate with respect to said hollow mounting tube;

a collector ring assembly positioned within said collector ring enclosure;

said collector ring assembly including a plurality of horizontally disposed electrically conductive slip rings stacked one upon the other and having a central opening;

said mounting tube extending upwardly through said central openings in said slip rings;

said conductive slip rings being operatively fixed to said mounting tube;

said collector ring assembly also including a brush support fixed to said enclosure for rotation therewith;

said brush support having a plurality of brush assemblies mounted thereon which are in electrical contact with said slip rings;

at least some of said electrical wires, which extend from said control panel, extending upwardly through said mounting tube and outwardly therefrom for electrical connection to said slip rings;

said brush assemblies having electrical wires secured thereto which extend outwardly from said enclosure for connection to electrical components on said span structure;

a monitoring device in said enclosure which monitors the span position or angle with respect to said center pivot structure;

a stationary communication device operatively secured to said mounting tube at the upper end thereof;

said monitoring device being physically interconnected to said mounting tube and said brush support;

a first ring gear rotatably embracing said mounting tube within said enclosure and which is rotatable with said enclosure;

said monitoring device including a second rotatable gear which is in mesh with said first gear;

said monitoring device being operatively fixedly secured to said mounting tube;

said monitoring device further including an electrical circuit which is driven by the rotation of said second gear as said enclosure and said first gear rotates with respect to said mounting tube.