PURPOSE: To attain transmission/reception by telescoping a telescopic built-in antenna and containing the antenna into the antenna container while being short-circuited to an outer conductor of the container so as to switch the built-in antenna into an outer antenna connected to the same point automatically.

CONSTITUTION: The built-in antenna 1a being telescopic and λ/4-λ (λ is wavelength) at the expansion and comprising plural stages of 1st, 2nd and 3rd rod conductor tubes 1a-1, 1a-2, 1a-3,... in slide contact with an inner conductor 1b-1 of an antenna containing part 1b, the antenna containing part 1b tightening and short-circuiting a knob screw 1a-4 at the tip of the built-in antenna 1a to the outer conductor 1b-2 in telescoping the built-in antenna 1a, and a coaxial cable 1c, λ/4 in length in total with the length of said antenna containing part 1b, are provided and the center conductor of the coaxial cable and one end of the sheath conductor are connected respectively to the inner conductor and the outer conductor of said antenna containing part, and the other end is connected respectively to a reception circuit section and a case. Thus, no switch means of the built-in antenna is required and the titled equipment is made inexpensive in the cost and miniaturized.