this is a cordless telephone, the base station is a standard dect base unit with pstn circuits, a 2g gsm module inside the base unit to support gsm network, the two networks all are standby for any incoming call, the priority to pstn for an outgoing call, and auto switch to gsm network when pstn line is unavailable.
feature list:
>dect technology, gap compatible, comply with dect6.0;
>2g gsm with 4 bands of 850/900/1800/1900mhz;
>pstn & gsm network dual mode standby;
>eco mode supported to reduce energy consumption and radiation;
>handset with 2 inch full graphic display;
>backup battery for base unit, and lion battery for handset;
>larger digits & characters in display;
>big button & alone sos button;
>loud speech & high quality conversion for handset;
>boost 40db for handset receiver;
>hac supported (hearing aid compatible) 
>room monitor (access & monitor the room environment from a mobile or telephone) 
>8 languages selectable in menu 
>up to 300 meters range outdoors and 50 meters range indoors;
>standby time up to 10 days & talk time up to 8 hours;
>two hours quick charge;
>backup battery in base unit;
>the priority to pstn for an outgoing call, and auto switch to gsm when pstn is unavailable;
>8 pre‐registered sos numbers, and voice prompts when sos call;
>advanced automatic line disconnecting (automatic disconnecting line when no voice or line reversal);
>contact id protocol (reports events to service center when battery low, lost link, lost power, lost line…).

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