[Hilo] How to use AT+KATH?

[Hilo] How to use AT+KATH? What’s the behavior when I use it?

Answer: AT+KATH is used to inform the caller the reason of disconnection. It’s used with ATH together when to reject an incoming call.
For example:

ATD1821155xxxx; —Making a voice call
OK
—Remote side does not answer the call and disconnect with AT+KATH=0 and ATH.
NO CARRIER —You may hear “…number is busy…” and then some busy tone "Du Du Du”
AT+CEER (Extended Error Report for the last call)
+CEER: “Cause Select:67 Cause:31” ----The cause is “User Busy”
OK

ATD1821155xxxx;
OK
—Remote side does not answer the call and disconnect with AT+KATH=17 and ATH.
NO CARRIER—You can hear “…number is busy…” and then some busy tone “Du Du Du”
AT+CEER
+CEER: “Cause Select:67 Cause:31” ----The cause is “User Busy”
OK

ATD1821155xxxx;
OK
—Remote side does not answer the call and disconnect with AT+KATH=18 and ATH.
NO ANSWER ----You hear nothing with the disconnection.
AT+CEER
+CEER: “Cause Select:67 Cause:18” ----The cause is “No User Responding”
OK

ATD1821155xxxx;
OK
—Remote side not answer the call and disconnect with AT+KATH=19 and ATH.
NO ANSWER
AT+CEER
+CEER: “Cause Select:67 Cause:19” ----The cause is “No Answer”
OK

ATD1821155xxxx;
OK
—Remote side not answer the call and disconnect with AT+KATH=21 and ATH.
NO CARRIER
AT+CEER
+CEER: “Cause Select:67 Cause:21” ----The cause is “Call Rejected”
OK

ATD1821155xxxx;
OK
—Remote side not answer the call and disconnect with AT+KATH=27 and ATH.
NO CARRIER
AT+CEER
+CEER: “Cause Select:67 Cause:27” ----The cause is “Destination Out of order”
OK