a limited-capacity transmission channel such as that used for transmitting telephone calls and faxes Compare broadband
Contemporary definitions for narrowband
noun
in data communications, a channel with bandwidth less than or equal to one voice and a slow data transfer rate, a low-capacity communications circuit or path; cf broadband
narrowband in Technology
networking A communication channel with a low data rate. [More specific?] The term is sometimes used for an Internet connection via a dial-up modem, typically at 56 kbaud, in contrast to broadband. (2003-10-15)