The secondary chip reader is hardware that can be ordered in complement with the 8" attendance clock or the DA2 door opener.
You then customize what should happen when you clock in on the secondary reader. For example, a door might be unlocked and ClockIN is recorded (when you have the secondary reader on the outside of the entrance door). You can find more about the secondary reader setup options here.
The secondary reader measures 123 × 86 × 15 mm, features an IP66-rated enclosure for outdoor use, and supports both 125 kHz RFID and 13.56 MHz NFC technologies.
Downloaded the order form here.