... telegraph (1844), invented by Samuel F.B. Morse (1 791 –1872) and Alfred Vail (1807–18 59) . Faxdevelopment began anew in the 192 0s, but it was not until the 197 0s that the ITU-T set internationalinteroperability ... dispersion, DWDM, EDFA, NZDF, and wavelength.Fx (Firefox) See Firefox. 199 Fx (Firefox)74570c06.qxd 9/ 11/07 12:21 PM Page 199 half-duplex (HDX) circuit differs in that it supports information transfer ... isachieved through frequency division duplex (FDD) with the downlink in the 91 6 94 9 MHz band and theuplink in the 871 90 4 MHz band. See also 1G, analog, cellular radio, downlink, FDD, FDMA, FM,...