They are solid state and digital, and have been for many years. They record on flash memory.
There is a third recorder option, the QAR, which many modern airliners have. It is also digital, and designed to have it’s memory module easily removeable and readable with ordinary desktop computers.
BA Flight 38, a 777-200ER built in 2001, had all 3 digital recorders.
http://en.wikipedia.org/wiki/BA038
http://en.wikipedia.org/wiki/Quick_access_recorder
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Durability in fire? Durability in water if case is breached, especially in depths of 20,000 feet?