https://www.doorbird.com/downloads/datasheet_keyfob1_en.pdf
Doorbird Intercom Transponder Key Fob 125 KHz, 10 p.
$70.15
(GTIN/EAN: 4260423860605, P/n: 423860605)
For A1121 IP Access Control Device
For D21x IP Video Door Stations and later
64 bit
Write-protected
Chip: TK4100
Material: ABS, waterproof, grey
10 pieces