Some of the features of these systems are considered advanced in modern practice and have been recently reinvented. An example of this is the error control codepoint 707 in the Edelcrantz code. This was used to request the repeat of a specified recent symbol. The 707 was followed by two symbols identifying the row and column in the current page of the logbook that it was required to repeat. This is an example of a selective repeat and is more efficient than the simple go back n strategy used on many modern networks. This was a later addition; both Edelcrantz (codepoint 272), and Chappe (codepoint 2H6) initially used only a simple "erase last character" for error control, taken directly from Hooke's 1684 proposal.