When the module is in manual mode for Operator selection, how is the PLMN selected?
The network selection is done by an algorithm which is provided in the 3GPP specification (3GPP spec 23.022 18.104.22.168.B ). According to it, this is how the process of searching for a PLMN in Manual Network selection Mode will work:-
The MS indicates whether there are any PLMNs, in all of its bands of operation, which are available. PLMN’s are presented in the following order:
ii) PLMNs contained in the “PLMN Selector” data field in the SIM (in priority order);
iii) Other PLMNs with received high quality signal in random order;
iv) All other PLMNs in order of decreasing signal quality.
If the user does not select a PLMN, the selected PLMN shall be the one that was selected before the PLMN selection procedure started. If no such PLMN was selected or that PLMN is no longer available, then the MS shall attempt to campon any acceptable cell and enter the LIMITED SERVICE STATE(emergency calls only).