diff --git a/forsyde-shallow.cabal b/forsyde-shallow.cabal
--- a/forsyde-shallow.cabal
+++ b/forsyde-shallow.cabal
@@ -1,5 +1,5 @@
 name:           forsyde-shallow
-version:        3.4.0.1
+version:        3.5.0.0
 cabal-version:  >= 1.10
 build-type:     Simple
 license:        BSD3
diff --git a/src/ForSyDe/Shallow/Utility/FIR.hs b/src/ForSyDe/Shallow/Utility/FIR.hs
--- a/src/ForSyDe/Shallow/Utility/FIR.hs
+++ b/src/ForSyDe/Shallow/Utility/FIR.hs
@@ -25,9 +25,14 @@
 firSY h = innerProdSY h . sipoSY k 0.0
     where k = lengthV h
 
+-- sipoSY :: Int -> b -> Signal b -> Vector (Signal b) 
+-- sipoSY n s0 = unzipxSY . scanlSY shiftrV initState
+--     where initState = copyV n s0
+
+-- | Create the tapped, or delayed signals for later consumption.
 sipoSY :: Int -> b -> Signal b -> Vector (Signal b) 
-sipoSY n s0 = unzipxSY . scanldSY shiftrV initState
-    where initState = copyV n s0
+sipoSY n s0 = iterateV n tap 
+    where tap = delaySY s0
 
 innerProdSY :: (Num a) => Vector a -> Vector (Signal a) -> Signal a
 innerProdSY coeffs = zipWithxSY (ipV coeffs)
diff --git a/test/Unit.hs b/test/Unit.hs
--- a/test/Unit.hs
+++ b/test/Unit.hs
@@ -1,4 +1,5 @@
 import ForSyDe.Shallow
+import ForSyDe.Shallow.Utility.FIR
 import Test.Hspec
 
 -- | Taken from <https://github.com/forsyde/forsyde-shallow-examples>
@@ -107,7 +108,10 @@
             [(1, 0, \[a] -> [])]))
 s2_test = signal $ [10..110]
 
-                 
+-- Test of FIR-filter
+test_firSY :: Signal Double
+test_firSY = firSY (vector [1.0, 0.75, 0.5, 0.25]) $ signal [1.0, 0.0, 0.0, 0.0, 0.0]
+
 main :: IO ()
 main = hspec $ do describe "ForSyDe.Shallow : " $ lab2tests
   where
@@ -124,3 +128,5 @@
         `shouldBe`(read "{1,1,1,2,2,4,4,8,8,16}" :: Signal Integer)
       it "SADF Anti Wind-up System" $ takeS 10 (test_antiWindUpSADF s2_test)
         `shouldBe`(read "{10,21,33,46,60,75,91,108,108,108}" :: Signal Integer)
+      it "SY FIR Filter" $ test_firSY
+        `shouldBe`(read "{1.0,0.75,0.5,0.25,0.0}" :: Signal Double)