| a stable telephone transmission system intended for measurement of loudness ratings and provided with:|
a sending system and a receiving system with handsets the defined sensitivity/frequency responses of which are restricted in bandwidth to typify those of sending and receiving systems of a complete telephone connection;
a device for calibrating, in terms of absolute units, the above sending and receiving systems;
an attenuator capable of adjustment to any desirable value
NOTE – The CCITT intermediate reference system is described in the CCITT Recommendation P48 from the Volume V of the Blue Book, 1989.