diff --git a/README.md b/README.md
index 71af40d..f1499b0 100644
--- a/README.md
+++ b/README.md
@@ -5,12 +5,13 @@ purpose
 
 Devices using the USB-C connector become more common, but most computer hosts still use USB Type-A (aka. USB-A) connectors.
 Thus USB-A to USB-C cable get widespread.
-But there is indication  on the cable about its intended usage: just charge the device, also allow data transfer, or even support fast data transfer.
+But there is no indication on the cable about its intended usage: just power or charge the device, also allow data transfer, or even support fast data transfer.
 The USB-AC cable tester identifies the capabilities of USB-A to USB-C cables.
 
 usage
 =====
 
+The USB-AC cable tester is powered by a CR1220 coin cell battery.
 Plug both ends of the USB-A to USB-C cable in the USB-AC cable tester and read the lights:
 
 - POWER: can be use to power a device (the VBUS and GND wires are present).