A password-protected power controller

The author describes the functional definition, design, construction, and operation of a password-protected power controller (PPC) for accessing data in a PC by telephone. The computer system includes a hard disk and remote control software (such as EasyLAN or CARBON COPY). The PPC connects serially between the external modem and the computer, plugs into wall power, and provides switched power to the computer system. Operationally, the PPC queries the caller for the password and, if a proper password is received from the caller, powers up the computer system. The remote-control software is loaded (by autoexec), and the PPC transparently passes all two-way serial communications. Monitoring of incoming data allows the PPC to power down the computer when the appropriate string is received. In local operation, the PPC provides manually controlled power and can be reprogrammed for different passwords and query strings. EEPROM (electrically erasable programmable read-only memory) is used for query and password storage. Techniques for reading from and writing to the 2816 2KX8 EEPROM are described, and the differences between EEPROM and NOVRAM (nonvolatile RAM) are discussed