Epson TM-P20 Technical Reference Manual page 52

Communication conditions using a USB interface
 Printer Class
 Vendor Class (initial setting)
Communication conditions using a Bluetooth interface
 Passkey (initial setting: 0000)
 Device name (initial setting: TM-P20_xxxxxx)
 Security (initial setting: Low)
 Auto Re-Connect with iOS device (initial setting: Enabled)
The device name is initially set to TM-P20_xxxxxx.
(xxxxxx refers to the last 6 digits of the serial number labeled on the back of your printer.)
Acceptable Characters
Item
Passkey
Device Name
52
Number of characters
4 to 16
1 to 31
Acceptable Characters
30H to 39H, 41H to 46H
(Indicates the number from "0" to "9" and "A" to
"F" in hexadecimal)
20H, 21H, 23H to 7EH
(Character code between 20H and 7EH and except
for the double quotation mark ("))