Case from life: NASA, Satellite Communications Center. In the backyard there is a functioning satellite on which they check the correctness of the command before sending it to the same satellite to Mars. Once the space explorers did not have time to make a check, and in a hurry sent instructions immediately to the Martian satellite. Then the satellite stopped responding. NAS sheep long scratched their heads - what's wrong? They decided to send the same message to the test satellite. What would you think? He installed the receiving antenna.