A synthetic resin guide for a chain, or other flexible transmission medium comprises a synthetic resin guide body having a shoe on which the transmission medium slides, and a slotted, plate-receiving portion integrally molded on the back side of the shoe for receiving a reinforcing plate. The invention also relates to a coupling and a simple connection for a counterweight. A second winding has a third port and a fourth port. The position engine may receive second measurements from an object within the physical environment, and generate a position location estimate for the object from the received second measurements and the mapped space.