A communication apparatus includes a first detection circuit which detects a call signal, and a second detection circuit detects information of a partner station sent between call signals. Dividing walls are provided between the chambers to maintain the value of the negative pressure larger than a predetermined value, especially for media with conventional widths. The base may be mounted to a tripod, steadicam, crane, boom or other device for supporting a platform used in stereoscopic cinematography. The magnetic masking layer is in a perpendicular magnetization state at temperatures that are in a proximity of TC2, and changes into an in-plane magnetization state at temperatures that are higher than the proximity of TC2. The code pages can be remapped as execute only in an alternate extended page table view.