During the Apollo 11 mission to the moon, there was a phone call where the POTUS at that time, Richard Nixon, was able to speak to astronauts Neil Armstrong and "Buzz" Aldrin. How was this possible?
Mission Control in Houston had a radio communication with the Apollo capsule as well as the Moon lander. A phone connection between the White House and Ground Control was established and connected to the radio transmitter and receiver. Of course the Deep Space Network with its three large antenna stations in Goldstone, Madrid and Canberra had to be used. To connect the overseas DSN stations to Houston, existing submarine communications cables and communications satellites like Early Bird were used.
Someone in Houston had to switch the transmitters and receivers for uplink when the President was speaking and for downlink when the astronauts were speaking. Of course the assistance of the personel at the DSN stations was needed to control the antenna direction and the power transmitters and high gain/low noise receivers at the dishes.
Continous speech connection between ground control and Apollo was necessary for the whole mission. Telephone connection to the White House was the easiest part.
Easy 101 answer for new readers who didn't know (I have kids asking):
It's called the Deep Space Network. They used really massive dish antennas [Google Photos].
Like the satellite TV antenna, but with a bowl as big as a football field!
Massive 34 meter and 70 meter antennas -- 100 footer and 200 footer dishes. Transmitting and receiving everything like sending space probe commands & receiving pictures and science data.
You can watch the Deep Space Network (DSN) transmissions at: https://eyes.nasa.gov/dsn/dsn.html
Real-time animated status of all the big antennas that the Deep Space Network (DSN) is using. It's fascinating, hypnotizing and mesmerizing.
The dishes are still in use today. The exact same big antenna that handled the phone call & live TV broadcast from the moon, now is used in receiving pretty pictures from the Mars Rovers.