MCHEETA Newest V802 Landline Telephone Call Blocking Device,Block Robocalls,Area Calls,Private Calls 100 groups outgoing blocked numbers(up to 16 digits).(For example,add "911" to the device,then children can't dail "911" out) 10 groups prefix blocked numbers(up to 10 digits) for incoming calls.(Like 800,801) Memory chip with call blocker, can store all numbers history and numbers with blacklist. 2 AAA batteries is required to display call id and keep time&date when your telephone line is within low voltage. Batteries not included. NOTE: There are three battery slots, however the third battery slot is a fake slot. 1000 groups numbers(up to 16 digits) capacity of blacklist numbers in totally. Block NO CID function:can block all calls without call id.(turn ON/OFF this function is at your freedom). Only when a number can be added to the BLACKLIST succeeded(The "SUCCEED" will show on the screen when a number is added to BLACKLIST succeeded,then this call blocker can work and can block them