1. Over current detecting circuit
   - Operation at the time of over load, such as a speaker terminal short.

2. DC voltage detecting circuit
  - Operation at the time when positive or negative DC voltage (+- 1.1V of detection level) has generated at output terminals.

3.  Muting circuit
  - Transient noise protection when power is ON-OFF.

4. Relay driver circuit (Drive current of 130mA at Max.)

5. Operation by dual power supply.