... perpendicular to each other. 3. The point,and the region in the vicinity thereof, at whichthree intersecting plane surfaces meet. Generally, the plane surfaces are mutually perpendicular. 4. The passband ... receiver. The transmitteris inside the device, and the receiver is containedeither inside the computer main unit, or in asmall box attached to the computer main unit bya cord. The box can ... respect to the horizonat the transmitting (TX) point, below which the ionosphere will reliably return the signal to the earth, and above which the ionosphere will notreliably return the signal....