The SONY SRS-T55 is a speaker that offers high-quality sound in a compact design. - Brand: SONY - Model: SRS-T55 - Condition: Fully functional Thank you for viewing. I bought this a long time ago to listen to MDs outside. I only used it a few times and have kept it stored at home. It runs on four AA batteries. Operation confirmed. The serial number has been recorded to prevent swapping.