An electrical apparatus constituting an electrical contactor or an auxiliary block adapted to be coupled to an electrical contactor, the electrical apparatus including on the one hand at least one terminal board comprising a case formed in an electrically insulating material and on the other hand a plurality of electrical contacts housed in the case and each having a fixed portion and a movable portion, each electrical contact varying, by displacement of its movable portion by an external control, between a closed configuration establishing an electrical contact between the mobile and fixed portions and an open configuration where this electrical contact is not established, the case comprising a main portion delimiting at least one pair of lateral housings offset from each other in parallel to a first direction and in each of which is mounted a connection terminal by direct plugging, at least one additional portion formed in a part separate from the main portion and delimiting at least one central housing in which is mounted another connection terminal by direct plugging, and mounting elements (25, 26) providing attachment of said at least one additional portion on the main portion in a functional configuration in which each connection terminal carried by said additional portion is located between the connection terminals mounted in the lateral housings delimited by the main portion and in which the connection terminals mounted in the lateral housings delimited by the main portion and each connection terminal carried by said at least one additional portion are disposed along a row oriented according to the first direction, each connection terminal by direct plugging comprising a contact spring mounted in the main portion or in said at least one additional portion and at least one support surface configured so as to guide the way in which the contact spring deforms and to limit its deformation, the support surface being positioned with respect to the spring contact by means of a relative displacement oriented according to the first direction, each connection terminal making it possible to establish an electrical and mechanical contact between an electrical conductor inserted in this connection terminal and an electrical conductor internal to the electrical apparatus itself electrically connected to the fixed portion of one of the electrical contacts, the main portion delimiting two separate pairs of lateral housings where the two lateral housings of each of the two pairs are offset from each other in parallel to the first direction, two lateral housings belonging to different pairs being offset in a direction perpendicular to the first direction, the lateral housings of the two pairs being arranged such that, when said at least one additional portion occupies its functional configuration, the connection terminals mounted in the lateral housings of the two pairs delimited by the main portion and the connection terminals carried by said at least one additional portion are disposed along two separate rows parallel and oriented according to the first direction, the case comprising two separate additional portions, each additional portion delimiting at least one central housing and in that the connection terminal mounted in said at least one central housing of one of the two additional portions belongs to one of the two rows and the connection terminal mounted in said at least one central housing of the other of the two additional portions belongs to the other of the two rows when the two additional portions occupy their functional configurations. the main portion delimiting two separate pairs of lateral housings where the two lateral housings of each of the two pairs are offset from each other in parallel to the first direction, two lateral housings belonging to different pairs being offset in a direction perpendicular to the first direction, the lateral housings of the two pairs being arranged such that, when said at least one additional portion occupies its functional configuration, the connection terminals mounted in the lateral housings of the two pairs delimited by the main portion and the connection terminals carried by said at least one additional portion are disposed along two separate rows parallel and oriented according to the first direction, the case comprising two separate additional portions, each additional portion delimiting at least one central housing and in that the connection terminal mounted in said at least one central housing of one of the two additional portions belongs to one of the two rows and the connection terminal mounted in said at least one central housing of the other of the two additional portions belongs to the other of the two rows when the two additional portions occupy their functional configurations.