The present invention discloses a contact center with speaker identification and verification capabilities. 2 or if information about the previous frame is unavailable, or codes the time lag using a variable-length coder if \u03c1\u2032 is not smaller than 0. A dilution gas is flowed through a dilution gas line which extends through the chamber to permit heating of the dilution gas by the heat in the chamber without mixing the dilution gas and the oxidizing gas in the chamber. Inter-exchangeable device covers carry different substrates to provide different functionalities of an electronic device with which the covers are used.