mode handsets where more than one RF PA may be operating simultaneously, for example a (relatively high power) LTE PA generating signal energy in parallel and proximate to (relatively low power) Bluetooth and/or WiFi transmitter. This is directly relevant to handsets using a mix of 'other technologies'. The trans- mitted signals need to be kept apart from each other and frequency plans need to be carefully validated to prevent intermodulation/mixing of these multiple transmit frequen- cies both into other transmit bands and into the receive bands supported in the handset. The receive bands could easily desensitise receive functions such as GPS or a DVB T or ATSC receiver. The resolution of these issues can incur substantial nonrecurring engineer- ing cost that need to be recovered in the RF BOM and/or absorbed over substantial market volumes. If RF functions in the phone are used in an either/or mode rather than simultaneously, there will be a need to 'mode switch' in the front end of the phone to provide a dedicated signal path for a particular service. Thus, the choice of a nonstandard band may have an impact on performance of other radio transceiver functions in the phone but will also require additional components. There can be several switching functions in the front end of the phone. 4.3.6 The TX/RX Switch for GSM There may (probably will) be a TX/RX switch that provides a time-duplexed separation between the GSM transmit burst and the receive burst received after a 'two-slot' delay (just over a millisecond). These devices will be switching at the frame rate (217 frames per second) and are designed to be reliable over 100 billion cycles or more. The switch speed and duty cycle of these functions makes them presently unsuitable for other technologies, for example MEMS-based switching solutions. Telecommunications Economies of Scale 4.3.7 Band Switching This switch function routes the signal to the appropriate SAW diplex filter that will band pass the wanted signal energy from that band and band stop unwanted