Abstract: The operation state of a servo motor is monitored and output to a user before automatic termination of power to the motor. A servo system includes a servo motor and a safety unit. The safety unit cuts off electric power to the servo motor when at least one of a speed, a position, acceleration, an amount of movement, a movement direction, and torque of the servo motor is outside a first operation range. Furthermore, the safety unit outputs a warning when at least one of the speed, the position, the acceleration, the amount of movement, the movement direction, the torque is within the first operation range, but is outside a second operation range that is narrower than the first operation range. User controls allow reduced operation when outside the second operation range.

Abstract: A safety unit is provided for this purpose, and includes a position determining unit, a speed determining unit, a logical product unit, and a stopping unit. When a rotation amount (positional data) of an encoder rotating in connection with a rotation shaft of a servo motor falls within a predetermined limiting range, the position determining unit outputs a command for stopping a motor to a logical product unit. When rotation speed of the encoder rotating in connection with the rotation shaft of the servo motor falls within a predetermined limiting range, the speed determining unit outputs the command for stopping the motor to the logical product unit. This control by the logical product unit requires a stop command from both the position and speed determining units. The logical product unit informs the stopping unit to stop the servo motor to a controller.

Abstract: A TV signal that was scrambled and transmitted from a CATV center is tuned by a TV tuner for a parent unit or a TV tuner for a child unit based on a command received from a microprocessor. The tuned TV signal is input to a descrambler provided in the parent unit. The descrambler descrambles the scrambled TV signal. The descrambled TV signal is input to a synthesizing unit for the parent unit or a synthesizing unit for the child unit. When the parent unit or the child unit cannot receive a desired pay channel program, the microprocessor causes a character generating unit to generate a message that indicates that a pay channel program cannot be watched. This message is synthesized with a TV signal by the synthesizing unit for the parent unit or the synthesizing unit for the child unit and then output to a TV receiver of the parent unit or a TV receiver of the child unit.