A garage door opener comprises at least two radio frequency transmitters, a radio frequency receiver, at least two memories, and a processor. One level of metal is devoted exclusively to non-local interconnect, and a layer of polysilicon is devoted to local interconnect, thereby saving significant space. A collection of virtual content can be viewed from a user connected to and being present within the virtual environment. In some embodiments, a receiver receives the cycle encoded signal and recovers data of the data input signal. A top surface of the spacer is higher than a top surface of the gate stack. The substance shutoff device comprises a catalyst portion provided in contact with one of an inflammable substance flow path and an oxidizer flow path; and a shutoff means, which operates by heating through a reaction between the inflammable substance and the oxidizer in the catalyst portion to shut down the communication of at least one of the inflammable substance and the oxidizer.