Not sure who the author is. The device is like the remote control. I can't remember the time period she goes back to but she goes several times.
At one point she is in jail. A doctor gives her the device to help stop her seizures.
At one point it stops working so she takes it to a repair shop and they think it is an actual garage door remote so they make it more powerful than it was intended. I think she gets stuck in the past.
It’s called Breakthrough (1970) by Ken Grimwood. Not in print anymore, unfortunately.
Twenty-six-year-old Elizabeth Austin has been cured of epilepsy by a new and daring experimental treatment. Tiny electrodes implanted in her brain, control her seizures and restore her to a normal life - free to repair a troubled marriage and resume an abandoned career. But as part of her operation, Elizabeth had agreed to have other electrodes implanted - in the so-called "silent" areas of the brain, whose functions are unknown to modern science. And when one of those electrodes is stimulated, Elizabeth is gripped by strange, shattering sensations. They are not memories - at least, not her memories.
The book is available to borrow from the Internet Archive.
