I have two separate 900 MHz cordless phones. I noticed that the handsets of both systems are losing sound volume over the years. They are barely audible now. Even the dial tone is faint. I wonder whether I can adjust something inside. Thanks.
My other phones are much louder. There is no problem with my hearing. The handset ringer volume is significantly lower than when they were new. The phones are very clean so there is no clogging. I liked the Panasonic 900 MHz phones because the base answering machine will call another phone if someone leaves message. They also don't interfere with my wi-fi router.
Battery could be the problem. I will test it. Thanks.
Replacement batteries for such phones are sometimes available at your local 'Dollar Store', for, ah, $1 (each).
Then again, a complete new set of FOUR cordless DECT 6.0 phones might be around $50 at your local Big Box store (ahem, Costco, ahem).
If you do decide to get new ones, just make sure they're the latest DECT and stay away from 900 MHz or 2.4 GHz or anything not DECT. You can wiki DECT to learn more.