eden and some of Norway and Denmark. Transmission is by the differentially coded binary information Typical receiver specifications are shown in Table 45.6. Each modulating a 1.187 kHz (+0.1Hz) tone which itself modulates a country has its own regulations set by its type approval authorities 57kHz (+6Hz) sub-carrier with maximum deviation of 3kHz. This (PTT's, FCC etc.) and they usually differ. Under the European 57kHz signal is transmitted as a sub-carrier with the FM programme Community Directives, harmonisation of specifications will occur signal. The sub-carrier is phase locked to the 19kHz stereo multi- and if a paging equipment is awarded the CE mark then it will be plexed pilot signal. approved for sale in any EEC market. This will save the costs of Because the programme operates in different areas on different multiple approvals and reduce time delays from the manufacturers. frequencies the receiver scans the 87MHz to 104MHz band every The regulations appertaining to paging receivers both in Europe 10 seconds looking for an MBS system identification code. The and North America will be restricted to EMC interference from the caller dials a four digit entry code, a subscriber 6 digit number and receiver and, in Europe, immunity from external interference to the further digits for options, such as a privacy code which is used to receiver. The European regulation also specifies a minimum im- prevent unauthorised callers paging the subscriber. A 52 bit paging munity to electrostatic discharge. The actual specification and limits code is sent which consists of two blocks of 16 information bits and of the new common European standard are due to be announced in 10 parity check bits. 1992. Operators of wide area systems will however still determine their own more comprehensive minimum performance require- ments specification, which the manufacturer's equipment will have 45.8 Paging receiver design to meet if he wishes to sell to them. The challenge to the paging receiver designer is always to package 45.8.2 Receiv