Constant-temperature type crystal oscillator

A constant-temperature type crystal oscillator comprising:

• a crystal unit for surface mounting comprising:
• a case main body, which has at least a bottom wall, and in which two crystal terminals and two dummy terminals serving as mounting terminals are provided on an outer bottom face thereof;
• and
• a crystal element that is housed in the case main body to be hermetically encapsulated with a cover;
• an oscillator output circuit comprising an oscillating stage formed along with the crystal unit and a buffering stage;
• a temperature control circuit that keeps an operational temperature of the crystal unit constant;
• and
• a circuit substrate, on which circuit elements of the crystal unit, the oscillator output circuit and the temperature control circuit are installed,
• wherein the temperature control circuit comprises:
• heating chip resistors;
• a power transistor that supplies electric power to the chip resistors;
• and
• a temperature sensing element that detects an operational temperature of the crystal unit,
• wherein each of the dummy terminals of the crystal unit is connected to a respective one of circuit terminals on the circuit substrate, and
• wherein at least one of the circuit terminals is connected to an electrically-conducting path, to which one terminal of the heating chip resistors is electrically connected, on the circuit substrate.