hone to phone and batch to batch Making Telecoms Work (a function of component volume) will mean that a significant number of phones will fail to pass basic RF performance production tests. This metric is known as 'RF yield'. There may be limited opportunities to rework and retest devices but essentially a 'low' RF yield will translate directly into an increase in the RF bill of materials for those phones that did actually make it through the production test process. By 1997 (5 years on), two things had happened. First, most vendors had been through two or three or more design iterations. This had delivered more safety margin in terms of designed performance over and above the conformance specification. Secondly, the major vendors had sufficient volume to negotiate with their RF component vendors to tighten component tolerances to reduce the handset to handset and batch to batch differences that had previously compromised RF yield. So in practice, a significant number of handsets were being shipped to market with a sensitivity of around - 107 dBm, 5 dB better than the conformance specification. Note that this did not apply to all handsets from all manufacturers and the spread between best and worst handsets was between 3 and 5 dB. At this point, GSM phones achieved a lower cost point, provided better and more consistent voice quality, longer talk and standby times, additional functionality and a smaller form factor than analogue cellular phones. Another ten years (2007) and the best handsets could be measured at 110 dBm (static sensitivity). There was still a 'best to worst' spread of between 3 and 5 dB between man- ufacturers and sometimes also between different handsets from the same manufacturer, but essentially GSM handset performance from an RF perspective was as good as it was ever going to get. The 'best to worst' spread still existed partly because of device and design differ- ences but also because not all handsets have sufficient production volume to realise a gain in performance. Note that over this pe