On-vehicle electronic device

An on-vehicle electronic device comprising:

• a main body which is fastened to a vehicle and has a first terminal;
• and
• an operation unit detachably mounted in said main body, said operation unit comprising a plurality of operation input keys, a second terminal electrically connected to said first terminal when said operation unit is mounted in said main body, and a detachment sense voltage generating means for generating at said second terminal a predetermined detachment sense voltage which value is not equal to 0 volt and is determined by a voltage applied from said first terminal to said second terminal,
• wherein the predetermined detachment sense voltage is set depending on a type of said on-vehicle electric device and said main body comprises:
• operation input key identifying means for identifying which one of the operation input keys is manipulated in a state where said operation unit is mounted in said main body;
• voltage detection means for detecting a voltage of signal inputted to said operation input key identifying means;
• and
• mounting detection means, coupled to said voltage detection means, for determining that said operation unit is mounted in and electrically connected to said main body if said voltage detection means detects the predetermined detachment sense voltage, and determining that said operation unit is not mounted in said main body if said voltage detection means detects a voltage other than the predetermined detachment sense voltage.

An on-vehicle electronic device, comprising:

• a main body which is fastened to a vehicle and has a first terminal;
• and
• an operation unit detachably mounted in said main body, said operation unit comprising a second terminal electrically connected to said first terminal when said operation unit is mounted in said main body, and a detachment sense voltage generating means for generating at said second terminal a predetermined detachment sense voltage which value is not equal to 0 volt and is determined by a voltage applied from said first terminal to said second terminal,
• wherein said main body comprises:
• a reference power source applying a reference voltage to said first terminal;
• voltage detection means for detecting a voltage applied to said first terminal;
• and
• mounting detection means, coupled to said voltage detection means, for determining that said operation unit is mounted in and electrically connected to said main body if said voltage detection means detects the predetermined detachment sense voltage, and determining that said operation unit is not mounted in said main body if said voltage detection means detects a voltage other than the predetermined detachment sense voltage and wherein:
• said voltage detection means comprises a first resistor connected between said reference power source and said first terminal, and a second resistor connected between said mounting detection means and said first terminal;
• and
• said detachment sense voltage generating means comprises a third resistor connected between said second terminal and a ground.