An application server includes a connection pool that specifies a number of allowable connections, and includes a backend failure detection mechanism and a backend failure recovery mechanism. At the first common-mode level, the offset-correction signal is based on a first value stored using a first offset-storage element. Second nonvolatile memory includes a history buffer. The chuck is heat shrunk onto the drill bit to form a unitary structure through direct bonding of the chuck with the drill bit. In this way, the problem of mutual interference in message reception and transmission that are performed by the UE in two systems on adjacent frequency bands is solved.