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How can I get my redstone to activate adjacent pistons?

I have 4 pistons with the following layout:

  T====
   PPPP

 P: piston
 =: restone wire
 T: redstone torch

When I put the redstone torch the pistons fail to activate and remain still. However if do the following:

   T
   PPPP

The first piston on the left activates as normal.

Shouldn't the redstone wire be enough for activating pistons?

I'm using version 1.2.5 SMP vanilla.