The SNE 4028S is a two-channel, crossover-protected expansion device with secure separation of control and output circuits. The device is located in a 45 mm housing and has eight enabling and three messaging current paths. If the power supply is on, the messaging current path Y03/Y04 is conducting. The device has a power unit that makes short-circuit-proof 24 V DC voltage available on terminals S11 and S21. The device has two safety channels, CH1 and CH2, which can be actuated through the terminal connections S12 and S31/S22, for example by a basic device. Control can thus take place through one or two channels and without crossover monitoring. As a result, applications up to PL e/Cat. 4 or SILCL 3 can be built up.