There was a downside to using the lower numbers: rotary phones worked by repeatedly shorting the connection to indicate to the switch which number it was, so on

There was a downside to using the lower numbers: rotary phones worked by repeatedly shorting the connection to indicate to the switch which number it was, so one "click" would be one, two clicks "two", etc. This led to many phones accidentally dealing "1" if they did not have their wires properly connected. It's the reason the emergency number is not 111 (They still received quite a few fake calls until newer switches came into use that only allow to tone dailing).