I thought that I was going to need to return some toll transponders from Bay Area FasTrak, but the message I got was that they were out of warranty and that I should discard them as I would any e-waste. As far as I can tell, they still work but they're no longer issuing this particular version of the transponder. But if I really wished to, I could mail it to them or drop them off at their office. They have a return address on them with a guarantee of postage paid. My one worry was that mailing them might subject me to tolls since I've heard of active toll tags being returned (or perhaps lost/found and dropped off in the mail) where they went past a tool bridge. However, the message I got was that they were disabled, so I guess that's not a risk since they're no longer active.
These were maybe state of the art in 2018 (I think that was the year I got them). They were smaller, had switches for number of passengers, and had a longer life battery. When the switch was set it would beep one to three times, which was useful to know if the battery was dead since it would stop beeping. The new ones don't use batteries. I'm guessing they use newer tech that doesn't require a battery and is powered through RF provided when driving near a receiver. My parents have one of these, which makes no noise but does have a switch. They've also noted that the oldest version will no longer work maybe in a year.
These were maybe state of the art in 2018 (I think that was the year I got them). They were smaller, had switches for number of passengers, and had a longer life battery. When the switch was set it would beep one to three times, which was useful to know if the battery was dead since it would stop beeping. The new ones don't use batteries. I'm guessing they use newer tech that doesn't require a battery and is powered through RF provided when driving near a receiver. My parents have one of these, which makes no noise but does have a switch. They've also noted that the oldest version will no longer work maybe in a year.