A communication system comprises a NAT device, a terminal device, and a communication control device. The housing enclosing moisture-absorbent material and deodorizing material. The transition piece frame includes an upstream surface, a downstream surface, and a radially inner surface extending between the upstream and downstream surfaces. Upon focusing on an infinite object point, the fourth lens group G4 moves in a locus opposite to that of movement of the third lens group G3 during zooming. The wordlength of the samples in the digital audio signal, expressed in number of bits, being equal to n, where n is an integer larger than zero, and the sampling rate is equal to 2p. The techniques disclosed herein are suitable for use in printers having print heads that differ in resolution from each other.