A communications system comprising: an on-vehicle electronic device; and a portable device that communicates with the on-vehicle electronic device, wherein the on-vehicle electronic device includes a signal creation part that creates a first signal that causes the portable device to enter a state of being able to carry out reception and a second signal to be transmitted to the portable device, a transmission number of times designation part that designates the number of times of transmitting the second signal, and a transmission control part that controls transmission of the first signal and transmission of the second signal, wherein the signal creation part creates the first signal that includes information for setting a period of time of causing the portable device to enter the state of being able to carry out reception in a state of noise being generated longer than one that is set in a state of noise not being generated, the transmission number of times designation part designates the number of times of transmitting the second signal in the state of noise being generated greater than one that is designated in the state of noise not being generated, and the transmission control part controls transmission of the second signal based on the number of times of transmitting the second signal designated by the transmission number of times designation part, and the portable device includes a reception waiting time setting part that sets, according to the period of time of causing the portable device to enter the state of being able to carry out reception included in the first signal from the on-vehicle electronic device, a period of time of entering a state of being able to carry out reception. an on-vehicle electronic device; and a portable device that communicates with the on-vehicle electronic device, wherein the on-vehicle electronic device includes a signal creation part that creates a first signal that causes the portable device to enter a state of being able to carry out reception and a second signal to be transmitted to the portable device, a transmission number of times designation part that designates the number of times of transmitting the second signal, and a transmission control part that controls transmission of the first signal and transmission of the second signal, wherein the signal creation part creates the first signal that includes information for setting a period of time of causing the portable device to enter the state of being able to carry out reception in a state of noise being generated longer than one that is set in a state of noise not being generated, the transmission number of times designation part designates the number of times of transmitting the second signal in the state of noise being generated greater than one that is designated in the state of noise not being generated, and the transmission control part controls transmission of the second signal based on the number of times of transmitting the second signal designated by the transmission number of times designation part, and the portable device includes a reception waiting time setting part that sets, according to the period of time of causing the portable device to enter the state of being able to carry out reception included in the first signal from the on-vehicle electronic device, a period of time of entering a state of being able to carry out reception.