Chua's equations:
ẋ = α[y − x − f(x)]
ẏ = x − y + z
ż = −βy
f(x) = m₁x + ½(m₀−m₁)(|x+1|−|x−1|)
Chua's diode f(x) is a piecewise-linear nonlinearity — the simplest circuit exhibiting chaos. The double-scroll attractor has two scrolls linked by a heteroclinic orbit.