Comprised of a hardwood base 1.1 meter long with laminated top and plastic feet. A meter long constantan resistance wire, 24swg, is stretched along a meter scale graduated in millimeters fitted on this base. Each end of the wire is firmly and precisely attached to plated copper strips. Three more copper strips are fixed parallel to the wire providing four gaps. Electric connections are made through 4mm socket binding post terminals. Supplied with a knife- edge jockey to make contact with resistance wire.