This device came in because a older women with a disability utilized this device and was so familiar with it, she did not and does not want to change. The owners said everyone they brought it to didn't know what it was and couldn't help her and could not fix it. Hmmm, anyway, it is as close to a TRS-80 and from that I know that if the battery is dead sometimes it didn't work (learned that in college!) It also some how lost its plug and charger, but thankfully the Medusa cabinet of ac/dc plugs is full, mission accomplished. So, new sub C pack series wired and soldered taped up and crammed in. Charged it up for 8 hours came in the next day and it works great and she can continue communicating her needs.