An efficient logging method and system is disclosed that can be used to recover from a failure in a transaction system. The unified messaging system can serve as a single interface to a number of messaging services provided by various messaging components which use different message types. The imaging device also may be fabricated to have a diagonal active area to facilitate contact of two adjacent pixels with the single column line and allow linear row select lines, reset lines and column lines. The active element time-divisionally drives the at least two light emitting elements during the display period of time, such that each said light emitting element emits the corresponding one of the colors per a sub display period of time.