rt2 respectively connected between the terminals 2b1 and 2b2 and between the terminals 2b3 and 2b4 of the second termination 2b a test device embodying the invention for conducting wires of bus comprises a first test module 1m also shown in fig1 this first module comprises a dc voltage power source sa having positive sa and negative sa terminals a first light emitting diode led drl a first switch 11 a second light emitting diode dv1 and a second switch i2 that are respectively connected in series between the terminals sa and sa the diodes dr1 and dr2 are forward biased in the direction from the terminal sa towards the terminal sa via the switches and are respectively associated with two different colors e g red r and green v the module 1m has four terminals 1m1 to 1m4 that are respectively connectable to the terminals 1b1 to 1b4 of the termination ib at the opposited end to the bus bu the terminals 1m1 and 1m2 are those of the switch il that are respectively connected to the cathode of the diode dr1 and to the anode of the diode dv1 the terminals 1m3 and 1m1 are those of the switch i2 that are respectively connected to the cathode of the diode dv1 and to the anode of the power source terminal sa the module 1m is intended to detect two types of anomaly in the bus bu i e electric discontinuities in the pairs of conductors pl and p2 and abnormal crossing between one of the wires of one of the two pairs pl and p2 and one of the wires of the other pair an anomaly of the first type is shown in fig2 i e an electric continuity fault in the first.