diff --git a/src/dsp.jl b/src/dsp.jl
deleted file mode 100644
index a301f413c..000000000
--- a/src/dsp.jl
+++ /dev/null
@@ -1,31 +0,0 @@
-ControlSystems.tf(p::DSP.PolynomialRatio, h::Real = 1) = tf(DSP.coefb(p), DSP.coefa(p), h)
-ControlSystems.tf(p::DSP.ZeroPoleGain, h::Real = 1) = tf(DSP.PolynomialRatio(p), h)
-
-DSP.PolynomialRatio(G::TransferFunction{<:Discrete}) = DSP.PolynomialRatio(numpoly(G)[], denpoly(G)[])
-
-function ControlSystems.TransferFunction(b::DSP.Biquad, h::Real = 1)
-    b0, b1, b2, a1, a2 = b.b0, b.b1, b.b2, b.a1, b.a2
-    tf([b0, b1, b2], [1, a1, a2], h)
-end
-
-
-"""
-    Gs, k = seriesform(G::TransferFunction)
-
-Convert a transfer function `G` to a vector of second-order transfer functions, the product of which equals `G`. `k` is a scalar gain.
-"""
-function seriesform(G::TransferFunction{<:Discrete})
-    Gs = DSP.SecondOrderSections(DSP.PolynomialRatio(G))
-    bqs = TransferFunction.(Gs.biquads, G.Ts)
-    bqs, Gs.g
-end
-
-
-function DSP.SecondOrderSections(G::TransferFunction{<:Discrete})
-    DSP.SecondOrderSections(DSP.PolynomialRatio(G))
-end
-
-function ControlSystems.zpk(p::DSP.ZeroPoleGain, h::Real)
-    z,p,k = p.z, p.p, p.z
-    zpk(z,p,k,h)
-end
\ No newline at end of file