How do you make a ultra-compact repeating signal for dispensers?

Probably the most compact design I know is like this:

W-W-B
W-R-T

W = Redstone Wire B = Any solid block R = Repeater T = Redstone Torch

Taken from minecraftwiki.

use a piston repeater

it works on the principle that a solid block transmits power but air doesn't moving the block disrupts/establishes the signal