The electromagnet is composed of two vertical, cylindrical coils wound around two arms of a U-shaped soft iron nucleus.
The mobile armature is set crosswise at the extremity of a lever that oscillates between two blades with an amplitude that can be regulated by means of two screws.
The two opposing springs are inside a hollow brass column: the extremity of one spring is attached to the top of the column and the other to the base of the column; they act on the lever by means of a small rectangular ring to which they are fixed with the other extremity.
A brass screw passing through the extremity of the column allows regulation of tension on the upper spring and a pin which can run along a vertical slit in the column acts as an index. A small lever, placed at the front of the device, allows regulation of tension on the lower spring and a movable needle indicates its degree on a semicircular scale.
Two horizontal clamping screws, fixed to the edge of the wooden base, communicate with the terminals of the electromagnet and are connected to the telegraph line for reception of dispatches.
Two other clamping screws, one of which in communication with the contact screw which is insulated from the column, and the other with the lever of the mobile armature, are for the purpose of retransmitting the dispatch to the receiver connected in series to the local generator.