A clock regeneration circuit includes a half-bit delay device that outputs a half-bit delayed signal B of a multi-level input signal A, a one-bit delay device that outputs a one-bit delayed signal C of the signal A, an adder, an attenuator that forms an threshold signal, an XOR circuit, and a BPF that outputs a clock signal with a frequency corresponding to a bit rate of the XOR signal. The recording head cleaning method for the ink-jet recording unit fills the ink channel with a cleaning solution and shakes the cleaning solution to clean the ink guides. In one embodiment, the acrylamide monomers disclosed here have a branched linking group on the polyether moiety which makes it possible to produce hydrophilic polyether modified silicone copolymers without the need to separate various by-products including, but not limited to, unreacted, isomerized polyether and associated high molecular weight by-products.