limited-distance modem[′lim·əd·əd ¦dis·təns ′mō‚dem]
A modem used only for communications within a building in order to improve the signal quality where a long distance exists between the terminal and the computer.
A device designed to transmit and receive signals over relatively short distances, typically less than 5 miles (8 kilometers). Abbreviated LDM. Also known as line driver.