Texas Instruments 600 Series User Manual page 6

Duracell Notice
The Texas Instruments Extensa 600 and 605 are designed to use
a Duracell DR35S or DR201 Rechargeable Battery. Texas
Instruments participates in the Duracell pro.link program. If you
would like to purchase additional batteries, please call the
Authorized Duracell Purchase Hotline at 1-800-603-8225. If you
have questions about battery performance, recycling a used
battery, or any other battery-related question, please call
Duracell Consumer Relations at 1-800-551-2355 (9:00 AM - 5:00
PM EST).