This technical report describes important background material used during the revision of IEC 61196-1:1995, Clause 14, Guidance for surface transfer impedance and screening attenuation limits for flexible r.f. cables. In this technical report, the relationship between surface transfer impedance (ZT) and screening attenuation (as) is given, also measurements of ZT and as are provided to show the correlation of mean screening attenuation between 200 MHz and 500 MHz and ZT at both 30 MHz and 300 MHz. The sensitivity of as to the relative velocity difference between the inner and outer system is shown. The cable data sheet should show the as values in a standardized form – Δv/v = 10 % and the characteristic impedance of the outer system is 150 Ω. It is also shown that a relative velocity difference change from 10 % to 40 % gives an improvement of 12 dB in screening attenuation.