A vacuum cleaner has a case including a dust chamber filtering dust included in air, an appliance chamber sucking the filtered air from the dust chamber and discharging the air through a discharge port, and a cord chamber storing a wound electrical cord. In one embodiment in a system comprising a plurality of devices connected to a network, a security module is provided for establishing security settings for regulating network access at these devices. To prevent possible friendly-fire incidents, troops would separate the two layers of the uniform patch, thereby releasing a controlled release of the Perfluorocarbon vapors. A method of making the yarn includes combining a glass filament and metal filament in a core wrapped by a sheath.