Knowles' first digital microphone was introduced to the market by in 2006. Pulse density modulation was a standard interface in CODECs and therefore a perfect interface to microphones for consumer electronics. In PDM, the voltage of the analog signal is encoded in the density of the logic ones. The lower the voltage, the less the density. The averaging of these values over time gives a precise digital representation of the analog output MEMS and it provides a number of benefits to a system.