When POTUS travels, the White House travels with him. Prior to the common use of cellular service, all calls were made via landline.
Part of that traveling entourage is a temporary WH Signal Switchboard. Prior to the actual visit, “switchboard” cards are produced to let the advance teams, USSS, traveling staff and local people know how to reach the temporary switch board.
These cards became presidential memorabilia items for collectors throughout the country. This collection is representative of travels from 1972 through 1990. (Nixon through GW Bush)
As a seller for the presidential memorabilia listed in my eBay store, I can attest that all the presidential and White House items are genuine and have originated from the White House. These items were acquired from an estate of a former presidential staffer who held positions with the National Security Council and the WH Advance teams traveling in support of the president, vice president, and Secretary of State, from 1972 through 1990. The owner of the estate will remain anonymous.