A phasor uses a series off all-pass filters with voltage (or current) controlled parameters. Jfets, LDR's, or transconductance amps can be the active elements. Then (at the output) the shifted (by a continuously varying amount (via a LFO driving the elements)) signal is mixed with the raw signal giving the comb filtering effect. A flanger uses a bucket brigade device to time delay the signal. The clock to the delay device is varied by a LFO and then the signals mixed as above.