A high-temperature-resistant component for an exhaust-gas treatment unit, an exhaust-gas treatment unit and a method for producing such a unit, include providing the component or the exhaust-gas treatment unit with a surface layer intended to prevent the formation of chromium carbide bridges during a brazing process for producing the exhaust-gas treatment unit. The multi-throw switch may be configured to direct signals received from the antenna between an amplification path that connects a receive terminal of the multi-throw switch to a receiver of the wireless communication system and at least one bypass path that connects an additional receive terminal of the multi-throw switch to the receiver. A hooking recess is defined in one of the sidewalls of the fixing portion. Consequently, the copper concentration in the region from the surface to the 30 \u03bcm depth of the quartz product can be controlled below 20 ppb, preferably below 3 ppb.