OLLGEN Dual Signal FSK/DTMF Phone Call Box Caller ID Display Without Call Blocker (White) EASY TO INSTALL:Adopting the advanced micro-computer controller design, automatic electronic calendar, adjustable LCD screen, No Call Blocker. CALLER NAME does NOT display on the device.Need to correctly connect the telephone line first, then you can set month/date/hour/minute. LARGE CAPICITY:Coming-in number and outgoing number calling back automatically, 30 Outgoing calls can be check, 100 coming-in calls memories. Mini Desigin:Power-saving design, with only two springs for battery connection as picture. It can properly work by two batteries.(It only need be worked by 2 AAA batteries even if it has 3 batteries spots .As one of them is useless).FSK / DTMF dual system automatically compatible, Adapt to multi-national standards and a variety of switches. ATTENTION: Not Compatible with Cordless Phones & Two Line Phone systems!! AND YOUR PHONE SERVICE MUST HAVE CALLER ID DISPLAY FUNCTION. NOTICE: When Users Install the Machine, Such As the Original Telephone Line Has Been Installed Other Terminal Equipment, Such As PBX, Password Control, Alarm Line, etc. Install This Machine In the front line, otherwise it will affect the Display of Incoming Calls.