The ATR1841 is a front monitor diode (FMD) which controls the laser power of the optical pickup for Blu-ray/HD-DVD, DVD and CD drives in one IC. With the Two-wire Interface (TWI) it is possible to fit the laser power for Blu-ray/HD-DVD, DVD and CD. Two bits are used to set the mode/gain level and 6 additional bits are used for gain trimming, within 6 dB. Entering sleep mode is also controlled via the TWI.