A dumb terminal is a component that allows access to a computer but does not have its own processing capability. They’re basically a keyboard and a screen. The TI Silent 700, so named because it was a dot matrix that printed relatively quietly, came out in this form in 1971 and had a thermal paper output instead of a monitor. It had a modem and accessed remote computers via, yes, a telephone. Enjoy the image of it plugged into a bona fide rotary phone.