A retractable scaffold support bracket is provided for mounting on the exterior surface of a concrete wall form. The electrical contacts are configured to be connected to a conductor of an electrical cable and include two sides, each side having a discontinuous contact positioning feature. On the basis of a comparison between the first recovered string and the second recovered string, a modified string is generated, in which erasures are located, and at least one second decoding attempt is carried out using the modified string. The upper unit includes a movable base, and a test plate having two rows of identical columns for engaging with the support plate.