Keypad for accessing e.g. room, has resistor chain connected to set of input keys and looped between two external voltage terminals, and load-current path, which is connected or disconnected between terminals based on external voltage level

摘要

The keypad has set of input keys (T1-T12), and resistor chain connected to the input keys. A portion of the resistor chain is looped between two external voltage terminals when the corresponding key is activated. A load-current path is provided between the two terminals and includes a load e.g. LED, and a Zener diode (D5). The diode connects or disconnects the path between the terminals based on the external voltage level. An independent claim is also included for a method for controlling of a keypad.