This AT&T TR1909 Trimline with caller ID/call waiting can be used either in tabletop or wall installation position, and requires four AA alkaline Batteries (not included) for battery-powered functions. The telephone can still operate with limited features when there are no batteries installed. The TR1909 also features a 13-number Memory for fast dialing and has a call log which can store up to 80 additional numbers with names. This AT&T 1909 telephone has a caller ID feature which supports caller ID with call waiting service - Caller ID services are subscriber services available from your local telephone companies for a fee.