A battery pack and a device, each including a CPU, communicate with each other. When the battery pack is mounted to the device, the CPU of the device reads a voltage V, output from dry cells built in the battery pack, from a positive terminal. The CPU sends a ready signal, and compares the read dry-cell...http://www.google.ca/patents/US5870025?utm_source=gb-gplus-sharePatent US5870025 - Power-supply apparatus and its mounting-completion indication method
