a. Apply RMA list and non-commercial invoice from service center.
b. Please declare delivery as normal USB barcode reader with the piece of $20 per unit and do not send back the accessories especially batteries if they are working fine. Please send back by TNT if it is possible since this would be easier for custom clearance. Fill and send RMA request sheet and non-commercial invoice. And send the faulty devices no more than 3 pieces in one packet.

There are null spots or dead zones in the read field. Moving the reader ensures that it is out of the null spots and all of the tags are interrogated, so movement or shaking sometimes is necessary in reading UHF tags.

An HID card is a smart card manufactured by HID GLOBAL. It stores and transacts data associated with either value, information, or both (not exclusive ID number, although it is an ID card) within the card's chip. An HID card is encoded upon printing, so a HID card can only be read by a HID reader.

Majorly there are 3 types.
Optical Sensors: use arrays of photodiode or phototransistor detectors to convert the energy in light incident on the detector into electrical charge
Capacitive Sensors: use an array capacitor plates to image the fingerprint
Ultrasonic Sensors: use very high frequency sound waves to penetrate the epidermal layer of skin.

Failure to read ultrahigh-frequency (UHF) tags happens more frequent than to read high-frequency (HF) and low-frequency (LF) tags, since UHF has a longer read range and utilizes a different means of tag-reader communication.
In UHF RFID systems, there can be null spots or dead zones in the read field in which tags cannot be energized. Please properly place the tags or move your reader so that all tags can be read.

The Electronic Product Code (EPC) is designed as a universal identifier that provides a unique identity for every physical object anywhere in the world, for all time. Stored on an RFID tag, EPC can be associated with dynamic data, such as the origination point of an item and the date of its production, to identify a specific item in the supply chain.

Can a 2D scanner read a 1D barcode?
---Yes

How to tell if a barcode scanner is for 1D or 2D barcode?
---By the scanning light. Light of 1D barcode scanner is lineal, of 2D is crossed.