This is an Aiphone TV doorphone set. The doorbell sound from the entrance unit and the voice from the main unit are not audible. On the main unit side, the image and audio from the sub-unit can be heard. Since the power supply was good, it can be determined that the main unit (JL-1M) is working fine, and the sub-unit (JL-DA) is faulty. (According to online research, the circuit board is likely to be the cause of the malfunction.) This is an item for those who can repair it or for parts. Please understand that the entrance unit is not functioning properly before considering this item. Thank you.