Abstract: An antenna switch (302) includes a radio terminal (R) and first and second antenna terminals (A1 and A2). When the second antenna terminal (A2) is unterminated, the radio terminal (R) is coupled to the first antenna terminal (A1). When the second antenna terminal (A2) is connected to a remote antenna system (304), the switch automatically couples the radio terminal (R) to the second antenna terminal (A2). Thus, the switch does not require a separate control terminal (C) and control signal to switch between the first and second antenna terminals. Instead, the switch is controlled by the presence or absence of a DC current at the second antenna terminal (A2). The remote antenna system includes a remote antenna (308) and a low pass filter (310) coupled between the remote antenna and ground. An alternate embodiment is described which includes a DC amplifier (402).

Abstract: A secure information broadcasting system including a central transmitting station for encoding data in binary form utilizing a keyword and transmitting a FM-SCA signal phase shift modulated by the encoded data. Each of a plurality of portable receiving terminals has an identification number stored therein. When a subscriber desires to display the broadcast information on his terminal, he enters a unique password which is combined with the identification number to generate the keyword. The keyword is utilized to decode the received binary data.

Abstract: A secure information broadcasting system including a central transmitting station for encoding data in binary form utilizing a keyword and transmitting a FM-SCA signal phase shift modulated by the encoded data. Each of a plurality of portable receiving terminals has an identification number stored therein. When a subscriber desires to display the broadcast information on his terminal, he enters a unique password which is combined with the identification number to generate the keyword. The keyword is utilized to decode the received binary data.

Abstract: A secure information broadcasting system including a central broadcasting station for encoding data in binary form utilizing a keyword and transmitting on one frequency a FM-SCA signal phase shift modulated by the encoded data. The encoded data is also supplied to one or more remote broadcasting stations, typically via telephone lines, where it is transmitted on a second frequency as a FM-SCA signal phase shift modulated by the encoded data. Each remote station transmits a relatively low power signal in a predetermined local area, such as an office building, while the central station transmits a relatively high power signal in a general area including one or more of the local areas. The general area signal is transmitted with a time delay relative to the remote stations. Each of a plurality of portable receiving terminals has an identification number stored therein.