Abstract: A test circuit for setting the synchronizatiom of a dual ignition system, particularly of an aircraft engine dual magneto system, having an oscillator circuit 3, two transformers 23, 24 connected to the oscillator circuit, said transformers receiving the oscillator signal at a cener-tap of their primary windings, in which the primary windings are connected at one end to a common potential and having at least two connections for connecting the test circuit to the ignition system to be tested, said two connections each being connected to the other end of the primary winding 23, 24. Secondary windings 27, 28 of the transformers 23, 24 are connected to indicator elements 29, 30.