Time-delayed feedback occurs in many systems and is particularly important at
high-speeds, where the time it takes signals to propagate through the device
components is comparable to the time scale of the fluctuations. A fascinating
feature of such systems is that seemingly simple devices can show exceedingly
complex dynamics. This has motivated the use of electronic and photonic
time-delay feedback devices in practical applications of chaos, such as ranging
and synchronization based chaos communications, for which microwave and
radio-frequency oscillators are needed. I will give an overview of our recent
work on high-speed chaos generators, synchronization, and chaos communication.