This section deals with baseband-to-baseband measurements for frequency division multiplex (f.d.m) telephony. These measurements are additional to those already given in part 1, section four of this publication: Measurements in the baseband, which are common to telephony and to television, for example group-delay and amplitude/frequency characteristics. All of the following measurements are carried out on a system loop either by establishing a transmission path through the transmitting and receiving chain via a test loop translater or by means of an i.f. loop.