Zte CDMA2000 1X EV-DO User Manual page 29

Call Waiting
During a call, you could select to answer the second incoming call, and then you could switch
between the two incoming calls.
Please firstly apply for this service from your local telecom operator.
During a call, if there is a new incoming call, a pop-up window will prompt you that you
have the second incoming call.
If you select to answer, please click "Accept waiting call" button. The previous call
won't be ended, but temporarily paused.
You could switch between two incoming calls by clicking "Switch call".
ZTE Corporation
CDMA2000 1X EV-DO Wireless Data Terminal User Guide
http://www.zte.com.cn