Carrying What Is Not Speech

Paper and text travel a path designed for speech. Fax sends images through an in-band modem; a short message rides in the signalling that sets up a call. This volume treats the two together, because both borrow a path that was not built for them, and in both the constraints of the path decide the shape of the coding outright. Neither the 1728 pixels across a scan line nor the ceiling of 140 octets came from anything about the content. It covers run-length and two-dimensional coding, the propagation of errors, the negotiation of capability in the call procedure, septet packing and the edges of the character set, and store-and-forward as a model of delivery.