ager synchronises with the incoming data stream and immediately turns off the radio circuits Because, in practice, transmissions may arrive at a receiver from until the pager's own time frame in the batch of 8 is approaching. any angle, the sensitivity specification is very often expressed in The radio is then turned on for say 10ms settling period followed by terms of the free field 8 position log average. For this purpose the a 64 bit period to read the address code words. If its address is found pager on pole is rotated and measured every 45° starting with E1. then a tone pager will beep and flash, and a numeric or alpha pager The sensitivity is said to be Em, given by Equation 45.1. will decode and display and/or store the message, before the radio section is once again switched off. (45.1) 45.8.8 Receiver programming Each receiver needs to be programmed with its individual address or addresses and with its feature options. This is carried out by a The relationship between face-on free field sensitivity and the 8 programming unit which can be used to programme the receiver by position average is fixed for a given receiver design, but needs to be the manufacturer, and to reprogramme it by the customer service determined by field measurement (a loop aerial will have significant engineer if desired. Each pager has a type of plug in programmable nulls at 90° and 270° with respect to face-on, whereas a helical memory. In the early 1980's this may well have been a bipolar array mono-pole will have a much more circular polar diagram). Thus a such as an 8 X 4 diode matrix with fusible links. Programming would correlation factor between the 8 position free field sensitivity and take place by passing currents of 1A through these links for a period the face-on figure in the TEM cell can also be established. of 10ms to form an open circuit. The disadvantage with this type of For some public wide area operator's specifications, pager on pole memory was that to change the programme a new memory had to measurements are call