1. An integrated circuit for receiving transmitted signals, comprising at least one variable integrated impedance means (R), a reference impedance (Rc) external to the integrated circuit having a given value and an automatic control means (3, 7, 8) for varying said variable integrated impedance means (R) to a value that is a function of said given value of the reference impedance (Rc), and further including at least one receiver connected by a transmission link to a transmitter, said transmission link including at least one transmission line, said receiver including amplification means for producing reception signals (s, s*) in response to the received transmitted signals produced on said transmission link by said transmitter, said amplification means including, for each transmission line, an amplifier including an adaptation impedance for adaptation to the transmission line and connected thereto, said adaptation impedance being constituted by said variable integrated impedance means (R), and said reference impedance (Rc) being a calibrated impedance having a value which is a function of said characteristic impedance of the transmission line, wherein the automatic control means includes a variable, integrated automatic control impedance (Ra) having a value which is a function of said variable integrated impedance means (R), and an impedance comparator means (3) for comparing the value of the automatic control impedance (Ra) to the given value of the reference impedance (Rc) and providing a variation signal (AR) for adjusting said variable integrated automatic control impedance (Ra) and said variable integrated impedance means (R).