Hi Peter,
The "Std" is the "Standard" version & the "Ext" stands for the "Extended life version" as shown below;
Battery | • Standard lithium-ion (Li-ion) battery life: up to 9.5 hours talk time and 180 hours standby • Extended Li-ion battery life: up to 13 hours talk time and 240 hours standby • Actual battery life varies significantly based on environmental factors and Bluetooth use |
From;
http://www.cisco.com/c/en/us/products/collateral/collaboration-endpoints/unified-wireless-ip-phone-7925g/data_sheet_c78-504890.html
Cheers!
Rob
