Relay, which is in particular intended to be integrated into a switch used for the purposes of interrupting an electric circuit in the case, when a difference between electric current in conductors (N, P) occurs, wherein such relay in the electrical context represents a resistance (R R) and inductivity of a coil (L R), via which the relay is electrically interconnected with a passive electronic circuit and indirectly also with a differential transformer intended for indication of a differential electric current in the area of said conductors (N, P), so that in the case of difference between currents in said conductors (N, P) due to the voltage generated in the differential transformer and in the passive electronic circuit a corresponding magnetic flux (Φ 4) is generated in said coil (L R), and wherein such relay in the mechanical contexts consists of a yoke, which comprises said inductive coil and a permanent magnet for providing a desired magnetic flux (Φ 1, Φ 2, Φ 3) in the area of said yoke, as well as of an armature, which is pivotally interconnected with said yoke in a pivot point and is, depending on energizing the coil (L R), either by means of said permanent magnet rest onto said yoke, or is by means of a force of a spring pivoted away from the yoke towards the actuating mechanism, which is located at appropriate distance apart from the yoke and is intended for activation of the switch in the sense of interrupting the electric circuit through said conductors (N, P), characterized in that the yoke is uniformly conceived and is cut or punched out of a plate or a strip consisting of steel or any other metallic alloy with pre-determined magnetic properties and comprises three arms (131, 132, 133), which are spaced apart from each other and protrude towards the armature, wherein their lengths are adjusted for the purposes of simultaneously abutment of said armature to all of them, and wherein - the first arm is adapted to receive the coil (L R), which is mounted on it in such a manner that said first arm extends throughout the coil (L R) and is surrounded by the winding of the coil (L R) extending along it; - the second arm is adapted to receive a permanent magnet, which permanently generates a magnetic flux and consequently a magnetic force, which is required for the purposes of abutment of the armature towards the said arms (131, 132, 133) of the yoke and which is acting in a direction opposite to the force of said spring; - the third arm is intended to support the armature and to provide a pivot point, around which the armature can be pivoted from its first position of abutment towards said arms (131, 132, 133) of the yoke to its second position, in which it abuts the actuating mechanism, which is located at appropriate distance apart from the yoke, and in that the armature is uniformly conceived and is made of a plate or a strip or a wire or any other rolled semi-product of a hot or cold formed preform consisting of steel or any other metallic alloy having pre-determined magnetic properties, and is in the pivot point pivotally interconnected with the yoke and comprises the first area, which is located in the one side of said pivot point and is adapted for simultaneously abutment towards all three arms (131, 132, 133) of the yoke, as well as the second cantilevered area, which is located on the other side of said pivot point and protrudes away from the yoke and in which a spring is mechanically connected to the armature. - the first arm is adapted to receive the coil (L R), which is mounted on it in such a manner that said first arm extends throughout the coil (L R) and is surrounded by the winding of the coil (L R) extending along it; - the second arm is adapted to receive a permanent magnet, which permanently generates a magnetic flux and consequently a magnetic force, which is required for the purposes of abutment of the armature towards the said arms (131, 132, 133) of the yoke and which is acting in a direction opposite to the force of said spring; - the third arm is intended to support the armature and to provide a pivot point, around which the armature can be pivoted from its first position of abutment towards said arms (131, 132, 133) of the yoke to its second position, in which it abuts the actuating mechanism, which is located at appropriate distance apart from the yoke,