Modem AT Command : COPS -- 與 operator 相關

AT+COPS 這個 command 跟 operator 相關。
可以用來：

1. 顯示目前註冊的operator
2. 選擇 operator 的方法：自動，手動
3. 列出所有搜尋到的 operator

例如： at+cops=? +COPS: (2,"Chunghwa Telecom","Chunghwa","46692",2), (1,"Chunghwa Telecom","Chunghwa","46692",0), (3,"VIBO","VIBO","46689",2), (3,"Far EasTone","FET","46601",0), (3,"TW Mobile","TWM","46697",0), (3,"TW Mobile","TWM","46697",2), (3,"Far EasTone","FET","46601",2), ,(0,1,2,3,4),(0,1,2) -- 實際上是連在一起，為好看，我加上分行。

每個 ( ) 代表一個 operator, 各攔的意思是：
( state, operator name - long, operator name -short, operator id, rate )

1. state : operator 的狀態。
   0 : unknown,
   1 : 可用
   2 : 目前註冊的 operator
   3 : 禁止使用
2. operator name , long, short, id : 分別是 operator 的三種表示法
3. rate : 網路型態：
   0 : GSM/GPRS
   2: WCDMA