n N channel system is given by a binomial 20.9 Overload distribution and that n is only exceeded with a probability of 1% (i.e. the value of n is not exceeded 99% of the time) as in Equation 20.34. g is the standard deviation of loud/soft talkers (see Table Elements of the network have to be able to transmit the peak signal 20.6) and N the system channel capacity. of the multichannel system load. The system overload requirements are dimensioned such that the probability of the peak busy hour transmission signal exceeding the n = N1+2.33( N1(1-1)) = (20.34) peak value of a sinusoid signal of power Pc is 0.01. P in dBmO is given by Equation 20.33 (CCITT, 1985, Supple- P has been calculated for some of the more important systems, ment 22) where t is the activity factor (see Table 20.6); L is the as in Table 20.8. 20/16 Frequency division multiplexing longest proposed international link is 25000km (CCITT,1985, Table 20.8 Examples of Peq G.103) and is constructed of a number of sub hypothetical links of typically 2500km. Number of channels 20.10.1 Noise contributions Peq (dBmO) Noise contributions are defined on a per channel basis in pWOp. 20.9.1 Overload measurement. Table 20.9 Design targets for noise contributions from open wire systems with 2500km circuit length The overload point is precisely defined according to one of two definitions, using charmonic/intermodulation products or using gain change. Equipment Number of Total noise equipments allocation Channel translation 2500pWOp 20.9.1.1 Harmonic/intermodulation products Line (group) frequency 2500pWOp translation CCITT (1985) Recommendation G223, defines the overload as: Line equipment noise 17500pWOp 'The overload point or overload level of an amplifier is at that value of absolute power at the output at which the absolute power level of the third harmonic increases by 20dB when the input signal Table 20.10 Design targets for noise contributions from to the amplifier is increased by 1dB.' metric pair cable systems, coaxial cable and radio systems with 2500 km