Owner's Manual
Page 117
... they have an incoming call when engaged on the Global System for cellular communication, guaranteeing compatibility between the various network operators. Call waiting Ability to another call. GSM (Global System for Mobile Communication) International standard for Mobile Communication (GSM) circuit-switched cellular phone connections and the Short Message Service (SMS). Glossary To help you understand...
... they have an incoming call when engaged on the Global System for cellular communication, guaranteeing compatibility between the various network operators. Call waiting Ability to another call. GSM (Global System for Mobile Communication) International standard for Mobile Communication (GSM) circuit-switched cellular phone connections and the Short Message Service (SMS). Glossary To help you understand...