Hello, I have this home telephone which is around the house for few years already and since nobody was interested in it I thought it is failing and the other members of the house just threw it away but when I shared that there will be good parts in it for scavenging(since I am electronics hobbiest) they said that it works but they just dont use it. Then I said to myself lets connect it and see for myself, but good thing that I am careful I first checked the dc jack and it said plus center and our home phone(current one) uses plus center as most of the trending electronic nowadays, but this Panasonic used minus center. So I bought new jack, wired it and connected the phone to my 12v battery, since it was written that accepts 12v. But now the phone is buzzing, I get it it is charging and the diode for charging is light, but I am afraid if there is internal fail. Can you guide me if there is fail or it is good since it charged for aroudn 10 minutes now? And if there is internal fail, where to look for it, like weak possible spots? Also is the middle pin of all three the minus one (on the charging nest for the phone headset)?