Automatic power supply system

In a power supply apparatus for electrically connecting an electric power supply to a plurality of boxes, including at least a cassette deck box, a stereo box and an audio box, which apparatus includes:

• an electric power supply line connected to an electric power supply;
• a cassette responsive selector switch connected to said electric power supply line, said switch being located in said cassette deck box and being switched by loading of a cassette into said cassette deck box and by unloading of the cassette from said cassette deck box;
• an automatic electric power supply circuit located within said cassette deck box, said circuit being connected to said cassette responsive switch and supplied thereby with electric power, depending on the state of said cassette responsive switch;
• a relay located within said audio box and connected by a control line to said automatic supply circuit, which circuit energizes said relay and thereby causes said relay to provide electric power from said power supply line to a circuit within said audio box in response to said cassette responsive switch being switched so as to provide power to said automatic supply circuit;
• and
• a first manually operable switch located within said stereo box and connected between said automatic supply circuit and a circuit within said stereo box;
• said automatic supply circuit including at least one transistor and a first diode, said first diode being coupled to said cassette responsive switch and to said transistor, said transistor being turned on and providing electric power to said relay and to a circuit within said cassette box when said automatic supply circuit is actuated by a forward voltage across said first diode;
• and
• said cassette responsive switch being switchable between a tape operating terminal and a stereo box operating terminal, said first manually operable switch in said stereo box being connected to said stereo box operating terminal of said cassette responsive switch through said first diode, closure of said first manually operable switch in said stereo box and switching of said cassette responsive switch to said stereo box operating terminal both being required to produce a forward voltage across said first diode and turn on said transistor and thereby provide electrical power to said relay and said circuit within said cassette deck box, the last-mentioned circuit being a control amplifier, a second diode being connected between said tape operating terminal of said cassette responsive switch and a point at which said transistor applies said electric power to said control amplifier, said second diode being oriented to positively block electric current flow from said point back toward said tape operating terminal of said cassette responsive switch, said cassette deck box further including a tape pre-amp connected between said tape operating terminal of said cassette responsive switch and said second diode, said tape pre-amp receiving electric power only when said cassette responsive switch is switched to said tape operating terminal,
• the improvement comprising a tuner box and a junction cable for connecting said tuner box to said power supply line and said control line, said tuner box including a second manually operable switch, a tuner, a tuner amplifier connected to said tuner and a third diode, said second manually operable switch being connected between said tuner amplifier and said power supply line through said cable, and said third diode being connected from the junction between said second switch and said tuner amplifier to said control line through said cable, whereby electric power is provided to operate said tuner amplifier and to energize said relay when said second manually operable switch is closed.