Components that will go into the weatherproof box include a timer, transforms, AC/DC converters, relays, a wireless network switcher, a USB HD, and a mysterious digital I/O box.

This miniature wireless router / network switcher allows the computer to talk to both cameras and outside world. It contains an antenna interface for future long-range wireless transmission.

This 2.5in USB HD is powered by USB bus. It is convenient to plug and unplug the HD because there is no need of external power supply. It is 100GB in capacity. We have bought two of them for swapping purpose.

The mysterious blackbox is a digital I/O box. It allows us to display the remaining HD capacity by adjusting the LED progress bar. We also can power on/off each camera individually by controlling the digital TTL relays. The red button is to allow the user to shutdown the system before swapping the HD.

Insider the custom-built digital I/O box. It contains 24 GPIOs and an IIC bus, which allow us to expand the system with different sensors in the future. It has a USB interface and is powered by USB bus.