Phasers
Phasers create a copy of the original signal and modulate that new signal's phase relationship to the original signal. When the two signals are reunited at the output, the modified signal which is moving smoothly in and out of phase, cause continuous cancellations and reinforcements at different frequencies throughout the modulating cycle.
Despite flanging and phasing sounding very similar they differ in a number of ways. A flanger works by having the entire signal time delayed, then added back on. A phaser's unique sound is produced by the differences in the output signal from the input signal. Not all of the parameters below would appear on certain types of units. For example, the MXR Phase 90 ( a guitar phaser pedal) only has 1 parameter - Speed.
Speed - This controls the LFO speed, also affects the modulation of the sound.
Depth - This adjust s the intensity of the phaser effect. High settings of depth combined with high settings of feedback produces almost snyth like results. Very far apart from the original dry signal.
Feedback - This controls how much of the modulated signal is fed back to the input of the unit. For units without a seperate resonance control, this can bring in that element.
LFO Waveform - In some cases, LFO waveforms can be chosen (sine, square etc) as they are used in the sound synthesis.