A protected switch unit is provided in a cassette tape recorder employing a single motor for driving a power transmission system for transferring a cassette holder and a power transmission system for loading and unloading the tape of the cassette loaded on the cassette tape recorder. The protected switch controls the motor for sequential cassette inserting operation and tape loading operation and for sequential tape unloading operation and cassette ejecting operation. A protective member for protecting the switch unit from dust is interposed between a circuit board having stationary contact terminals and a machine element of the power transmission system, carrying a movable contact terminal so as to seal the switch unit from dust.