The leaf nodes connected to the gateway are the units where the remote sensors and/or the control unit interfaces are located. The physical hardware is very simple and just needs the following parts: the SPR module, the sensors and units to control connected to the SPR module via a local PCB bus, a power source (typically a small battery), the PCB, an antenna (either an external antenna or a PCB antenna), and the enclosure (the mechanical box). This design is very simple to actualize for an electronics engineer with some hardware experience. If a PCB antenna is desired, then an RF designer also needs to be involved.