Abstract: A service information receiving apparatus (1) for receiving scrambled charged service information transmitted as being multiplexed on an FM broadcast radio wave from an FM broadcasting station (3) causes a control section (43) to perform a predetermined arithmetic operation by using a variable key as one of descramble keys affixed to the scrambled charged service information received by a service information receiving section (40) and a half-fixed key as one of descramble keys, which is stored in an IC card (2) detachably attached to a receiving apparatus main body, thereby preparing a new descramble key, which is used to descramble the received charged service information.

Abstract: A communication system can maintain high security in communication between a communication apparatus and a terminal. The communication system includes the communication apparatus and the terminal provided with a memory unit for storing data for specifying function of the communication apparatus. The communication apparatus and the terminal include random number generators for generating random numbers, encryption/decryption key preparing units for preparing encryption/decryption keys on the basis of both random numbers and generated by the respective random number generators of the communication apparatus and the terminal and a secret key held in common by the communication apparatus and the terminal, and encryption/decryption processing units for encrypting or decrypting communication data between the communication apparatus and the terminal containing the data by means of the encryption/description key, respectively.

Abstract: A liquid crystal projector which comprises image light-refracting means for deflecting the direction in which ligh beams permeating liquid crystal display panel is projected on a screen by an angle corresponding to the suitable viewing angle of the liquid crystal display panel, and wherein image light thus refracted is thrown on a screen in an enlarged form by means of projection lens systems.

Abstract: A television video signal A/D converter apparatus in a liquid crystal television receiver has an A/D converter for A/D converting a television video signal. Upper and lower reference potentials for determining an operating voltage amplitude are supplied to the A/D converter from a reference potential generator. The upper and lower reference potentials are divided at a given ratio by a resistor so as to fix an average potential of the television video signal at a constant value using the potential at the dividing point as a bias potential, and thereafter the television video signal is supplied to the A/D converter.