RFID / Barcode / Magnet stribe / TAGs / POS

125kHz TAG
rectangular, transparent plastic
Dim: 20 x 25 x 0.7 mm
TAG is waterproof

RFID UHF 865MHz PVC Bracelet
One-off closure
Adjustable size
Waterproof
Operating temperature: -30 ~ 75 ° C
White
Width 2.7 mm
Length Shared 100 mm
total length 278 mm

Ceramic UHF Take against metal
survive Temp: -40 - + 250 ° C Short-lived
can autoclaved several times
operating temp: -40 - + 85 ° C
Alien Higgs-3 chip < Br> Objective: 10 x 5 x 3 mm
Weight: 0.8g
reading distance: Up to 3 meters (1 watt reader)
suitable for location against metal - can give better reading distance
read / write : 100,000 times
Data Storage: Over 10 years
IP68 

Dallas iButton tag med unikt indkodet nummer

Passive 865 MHz RFID PVC TAG
0 - 2m depending on antenna gain
TAG format - Adhesive Paper
Protocol: ISO 18000 6C (R / W) - 96bit EPC / 512bit user
TAG ID UID in other sector.
Dimensions: 121 mm X 44 mm X 0.4 mm
weight: 2 g
Operating temperature: -10 to +60°C.

Magnetic card reader - HID. Keyboard emulation
Magnetic card reader for PS2
Can be connected via USB with adapter
USB adapter may require a restart of the PC!
PS/2 to USB adapter included
A reader head / tone head
Black
Works with OS up to and including Win 10
Can read Æ, Ø, Å. oh, oh, oh
Suitable for clinics for reading health cards
Dimensions: L 137 x H 50 XB 49 mm

Tag, key ring
target: 35 x 2 x 4 mm
with engraved UID code
tag is waterproof

125kHz RFID TAG
credit card size 0.8 mm
sequential ID
TAG is waterproof

Mifare Classic 1K RFID Tag
Reading distance: 0 - 10 cm
ISO14443A
1 Kilobyte Memory
768 byte free in 16 sectors / 4 blocks / 16 bytes
UID code is factory programmed - Cannot be changed
Frequency: 13.56MHz
Material: ABS, IP68
credit card format
Dim: 85.7 x 54 x 0.8 mm

ISO magnetic card with High Coat magnetic stripe.
Can be delivered with color printing for extra payment.
Cards with the same print for quantities of 25 or more. and up.
Price is per piece.

Dual band RFID card reader for USB - Decimal
10 characters decimal (ASCII) - 40bit
125 kHz, 13.56 MHz, NFC
125khz: EM4001, EM4002, EM4200
Mifare: ISO 1443a / B / 15693
HID - Keyboard Emulation
Reading distance: Up to 10 cm
Align via USB
USB interface
ID Format setting with DIP switches - see Table
Operating Temp. -25 ° to + 70 ° C
target: 88 x 56 x 18 mm

125kHz RFID TAG
For key ring
Dimensions: 37 x 30 x 8 mm
with printed UID code
TAG is waterproof

UHF RFID Take with Strip
Frequency: 860-960MHz
Blue
Width 30 mm
Length Sign 110 mm
Height / Thickness 12.5 mm
Length Strips 215 mm
Total Length 325 mm

125kHz RFID TAG for adhesion
Dim: 20 x 3 mm
3M tape
black
TAG is waterproof

Passive 865 MHz RFID PVC Tag
0 - 10 m depending on antenna Gain
ISO Short format 86 x 54 x 0.5mm
protocol: ISO 18000-6C (R / W) - 96bit EPC / 512bit User
Tag ID UID in the second sector.
Read and write: 100,000 times
Material: Paper
Operating temperature: -20 - + 85 ° C

Dual band RFID card reader for USB - Decimal
10 characters decimal (ASCII) - 40bit
125 kHz, 13.56 MHz, NFC
125khz: EM4001, EM4002, EM4200
Mifare: ISO 1443A/B/15693
HID - Keyboard Emulation
Reading distance: Up to 10 cm
Align via USB
USB interface
Dip-SW to ID format setting - see Table 
Environment: IP67 Waterproof, outdoor mounting
operating temp. -25 ° to + 70 ° C
target: 88 x 56 x 18 mm

Mifare Classic 1K RFID Tag
Reading distance: 0 - 5 cm
ISO14443A
1 Kilobyte Memory
768 byte Free in 16 sectors / 4 blocks / 16 bytes
UID code is factory programmed - Cannot be changed
blue key ring
Frequency: 13.56MHz
Material: ABS, IP68
DIM: 40 x 32 x 4 mm

NOTE: Contract with Danbit A / S and User Agreement with service supplier MUST be established before purchase!

Payment system with touch display.
accept contactless, chip, magnetic stripe and mobilepay.
GSM antenna connector MMCX to 6 digital outputs. Can be programmed with the time difference when paying. To 6 deaktiveringsindgang2. Can be configured to disable the machine
can be connected to a vending machine, washing machine, door, etc.
Web-based control panel.
Communications Internet or WiFi or 4G
Support for setup can be purchased.
Supplied with SIM card (4G)
Supply voltage: 10 - 24VDC, 10 - 42VAC / 2Amp (power supply included)

TAG, cylinder, black
4.5 x 30 mm
TAG is waterproof

Keyboard emulation: 8 digits, 32bit ASCII, Decimal
Frequency: 13.56MHz Mifare Ultra Light
Versions: Mifare S50, S70, ISO15693, ISO14443A/B
Power supply: 5VDC from USB port
Operating temperature: -10 - +75°C
Reading distance: 5 ~ 15 cm
Cable: Mount the USB cable on the back
Dimension: 118 (L) x 75 (W) x 17 (H) mm
Weight: 250g ± 10%
Waterproof IP67, wall mounting

Frequency: 860-960MHz
PVC / PET
ISO18000-6C (EPC GEN2)
Dimensions: 86x54x0.8mm
Operating temperature: -25C - 85 degrees

125kHz RFID TAG with screw hole
50 mm diameter x 2.5 mm
suitable for guard rounding as checkpoint
Ask 64 bits,
Manchester Encoding; 10 Digits in HEX

Passive 865 MHz RFID PVC Tag
0 - 2 meters Depending on Antenna Gain
TAG Format 55 x 10 x 1.6 mm - for textile - Flexible
protocol: ISO 18000-6C (r / W) - 96bit EPC / 512bit User
TAG ID UID in the second TAG sector.
Weight: 1 g
Operating temperature: -20 - +50°C,

TAG, round piece, self-adhesive
1.7 x 25 mm
TAG is waterproof

Waterproof RFID reader
only with Wiegand Interface
Connect to access controls with Wiegand
TAG Type: EM / Mifare
Reading distance: 5.8 cm
IP68
Frequency: 125kHz / 13,56MHz
LED and Buzzer
Cable out from the back
Detachable Backpiece
Supply Voltage: 12VDC
Dimensions: 86 x 86 x 22mm

125 kHz RFID TAG
Dim: Ø25 x 3 mm
TAG is waterproof

BEMÆRK: Kontrakt med DANBIT A/S og Brugeraftale med serviceleverandør SKAL etableres før køb!

Betalingssystem med touch display.
All-in-one med POS og Data-kommunikation i samme hus
Accepterer kontaktløse kort og MobilePay.
GSM antennestik MMCX stik
6 digitale OC. pulsudgange til automat/vendingmaskine, maskiner, døre etc.
6 digitale indgange, inhibit, for at stoppe køb ved mangel/fejl
Konfigureres via platform med priser og funktioner
Kan tilkobles en salgsautomat, vaskemaskine, dør, osv
Web-baseret eller MQTT Cloud
Kommunikation: LAN eller 4G
Support til opsætning kan tilkøbes.
Leveres med SIM kort klar til funktioneopsætning
Forsyningsspænding: 10-24VDC, 10-42VAC / 2A (PSU medfølger ikke)

Mifare reads with USB
13.56MHz
USB HID (plug and play)
Powered from USB
Additional purchases from Decimal to HEX, normal or reverse
Additions with start and or stop character
Supports: ISO14443A, ISO18092 FeLiCa tags
Dimensions: 100 x 65 x 23 mm
Material: ABS
REMEMBER: Order the desired version - additional purchase

Keyboard emulation: 10 digits, 40bit ASCII Decimal
frequency: 125 kHz EM 4001/4002
Power supply: 5VDC from the USB port
Operating temperature: -10 - + 75 ° C
reading range: 5 ~ 15 cm
cable length: solved USB cable
Dimension: 118 (L) × 75 (W) x 17 (H) mm
Weight: 250g ± 10%
Desktop - desktop model

RFID with QR code reader
125kHz EM400x
13,56MHz Mifare Ultralight
Built-in buzzer for audio notification
can read multiple formats
With CPU watchdog
Power supply: 12V DC
Output: RS232, RS485, Wiegand 26/34 bits

Net adapter 12V, 1A - Switch mode
Output: 12VDC / 1Amp
230VAC input
Power plug: 5.5 / 2.5 mm
Cable color: + Red, - White

RFID 13.56MHz Mifare reader
Looks like a USB stick
ISO14443A standard
5VDC/100mA from USB port
USB 1.1
UID code as 40 bit HEX. HID to USB port
40 bit UID
Reads the same code once on presentation
Automatic CR and line change
Reading distance up to 2 cm
LED tri-color
Dimensions: 70mm x 20mm x 9.8mm
Weight: 18g
Reading speed: less than 100ms

Passive 865 MHz RFID PVC tag (860 - 960MHz)
0 - 10m depending on antenna gain
ISO short format 86 x 54 x 2 mm - card holder available
Protocol: ISO 18000-6C (R / W)
Card ID in other sector.
Operating temperature: -25 ℃ ~ + 65 ℃

Keyboard emulation: 10 digits, 40bit ASCII, Decimal
Frequency: 13,56MHz Mifare Ultralight
Versions: Mifare S50, S70, ISO15693, ISO14443A / B
Power supply: 5VDC from USB port
Operating Temperature: -10 - + 75 ° C
reading range: 5 ~ 15 cm
cable length: solved USB cable
Dimension: 118 (L) × 75 (W) x 17 (H) mm
Weight: 250g ± 10%
Desktop - desktop model

Module with 2 relay outputs
5VDC from optically isolated digital input
GND, VCC, IN (digital input)
COM, NC, NO
Max load: AC 250V / 10A DC 30V / 10A - non inductive load!
REMEMBER THE RIGHT CABLE FOR YOUR NAYAX TERMINAL!

125kHz EM TAG with magnetic stripe
credit card format
0.8 mm, incl. Magnetic stripe
TAG is waterproof

RFID Mifare reader
13.56MHz, Mifare, Felica, Desfire, Ultralight, Felic
Reading distance up to 3 cm
RS232 or Wiegand 26 Interface
for wall mounting
LED and Buzzer
Supply voltage: 5 - 18VDC
cable from back
Target: 78 x 43 x 15 mm

Passiv 865 MHz RFID holder til RFID865TAG-W

Magnetic card 1/2/3 Tracks reader
RFID 13.56MHz reader / writer
IC Cards reader / writer
NFC reader
Does not support special characters like æ,å,ø...
Dimensions 160mm x 45mm x 45mm
SDK examples for developing applications
Win10, Win7, Vista, Win2000, XP, Linux

RFID Copy Reader / Writes to T5577 RW Tag
interface: USB
Work voltage: 5 VDC
Work current: 200mA
Standby Stream: 50mA
Normal current: 100mA
125kHz, 13,56MHz Mifare / NFC
Compatible with CCID and PC / SC
IC / ID Dual Frequency Replication
Supporter ID125K, 8800, 5200, 4305, 5577, 8265 Card
Support UID, Fuid, Cuid, UFUID
IC Semi-Encrypted Card, IC Full Encryption Card
Dim: 108 (L) x 68 (W) x 12 mm (H)

RFID 125kHz reader with RS232
EM 4xxx Standard Tag (40 bit HEX)
Mounting in Ø 31 mm Hole
Length from Resess: 27 mm
Resess Width: 40 mm
RS232 , 9600, N, 8, 1
9 - 12VDC / 50mA
Temperature: -10 - + 70 ° C
Material: PBC
IP54 from front

Reading distance: Up to 5 cm
Frequency: 13.56 MHz
Read Mifare Ultralight and Mifare F1 Standard Tag
Mifare 1024/4096 byte, Ultralight 512bit, ISO 14443A
3 in 1 interface : Wiegand, MSR ABA TK2 and RS232
LED and Buzzer
Quick Data Transfer
Weatherproof, ABS
Cable Length: 90 cm
Cable is not terminated with DB9
Easy to install
Supply: 5 - 18VDC (Liniary PSU)
Dim: 83 x 47 x 16 mm

1D wireless barcode scanner with USB RF dongle
wireless row side is typically 30 meters
built-in memory for approx. 400 scans
Supports all common 1D barcodes
Radio Technology: Zigbee

RFID reader for RS232 / RS485 / Wiegand
IP64
Range up to 60cm
Serial communication to / from PC
Relay output (24VDC / 2A) Serial Enabled from PC
Baud Rate : 9600, 8, n, 1
Dim: 210 x 210 x 28 mm
Extended temperature -10 - 60°C
supply: DC 12V, 350mA

RFID TAG mounting on metal
Passive 865 MHz RFID PVC Tag (860 - 960MHz)
0 - 5 meters depending on antenna Gain
TAG Format 138 x 30 x 5 mm
protocol: ISO 18000-6C (R / W) - 96bit EPC / 512bit User
TAG ID (UID) in the second sector on the roof.

Take, credit card size 0.8mm.
Tags are waterproof

Trigger til at åbne pengeskuffer med Epson, Citizen eller Star interface

reads ISO tracks 1, 2 and 3

RS232 interface

USB 2 x PC splitter
2 x DB9 special cable output (DB9 to USB)
1 x RS232
USB Power (5VDC)
Speeds from 1200bps to 115200bps with select
OS support: Windows OS, MAC OS X, Linux
Incl. 2 pcs. DB9 male to USB-A male cable 1,2m
Operating temp. 0 - + 50 ° C

125khz RFID reader for outdoor mounting on wall
sealed with hardened epoxy - cable mid rear
EM4000 125khz RFID Reader for wall mounting
reading distance 0 - 5cm, depending on roof size
40 bit code, 10 digits ASCII (Decimal)
RS232, only TX. GND
9600, 0 Start, 8 Data, 1 Stop, Non Parity, FLOW: HW
Wiegand 26bit format
LED Indicator and Buzzer Control Manager
Supply voltage: 12VDC / 200ma
Cable length 1 meter (8 Core)
Goal: 114 x 46 x 13 mm

Dual band RFID card reader for USB - 10 Decimal
125 kHz: EM-Marin EM41xx, EM4200
13,56MHz: Mifare - ISO14443A
HID - Keyboard Emulation
Reading distance: 5 to 8cm
Powered by USB
USB interface
operating temp. -10 ° to + 70 ° C
dimensions: 98 x 63 x 10mm (L x B x H)

MDB Male and Female
EXT-MCR
TEMP
GND
DOOR OPEN
DEX Male and Female
RS232

Kan indsætte diverse formateringstegn, f.eks. linjeskift.

Programmerbar magnetkortlæser med PS/2 interface. Lysdioder sikrer optisk kvittering, akustisk lydsignal ved korrekt aflæsning af magnetkort.

Universal electric car charging stand for all EV vehicles
Allow two electric cars to charge at the same time
Smart design
Dynamic management of charging
Interface protocol: OCPP 1.6
Payment for parking and charging by payment card
Monthly fees apply
AC Input 230-400 VAC +/- 10 (2 or 3 phase)
Total Power output 2 x 22kW / 2 x 32A Max (load sharing)
Payment: Payment card, Google Pay, Apple Pay (option: MobilePay)
Communication: 4G
IP degree: IP55
Operating temperature: -25 C° to 55 C°
Dimensions: 520 x 360 x 260 mm
Charger cable not included. The user uses the cable that comes with their car.

Keyboard Emulation: 10 digits, 40bit HEX
Frequency: 13.56MHz Mifare Ultra Light
Versions: Mifare S50, S70, ISO15693, ISO14443A / B
Power supply: 5VDC from USB port
Operating temperature : -10 - + 75 ° C
Reading distance: 5 ~ 15 cm
Cable length: Solved USB cable
Dimension: 118 (L) x 75 (w) x 17 (h) mm
Weight: 250g ± 10%
desktop - table model

Payment system for vending machines, doors etc.
Accepts contactless & nbsp; chip, magnetic stripe and MobilePay
GSM (SMA) and LAN (RJ-45)
2 x digital outputs. & nbsp;
1 x deaktiveringsindgang. Can be configured to deactivate the machine
Can be connected to a vending machine, washing machine, door, etc.
Web-based control panel, can be operated over the Internet
Support for setup can be purchased
Comes with SIM card
User agreement with service provider is required

Opsætnings softwaren virker kun på en Windows XP pc der har en PS2 keyboard port

20 pcs. Mifare Transponder / TAG to Keychain
Mifare Classic 1K RFID TAG
Reading distance: 0 - 5 cm
ISO14443A
1 kilobyte Memory
768 byte free in 16 sectors / 4 blocks / 16 bytes
UID code is factory programmed
Gray key ring
Frequency: 13.56MHz
Material: ABS, IP68

Dimensions: 119.6(L) x 76.6(W) x 15(H)mm

1D, 2D barcode reader
Wireless 2.4GHz via base station (supplied) or USB-A to USB-B cable (included)
Reading distance: 10mm-700mm
Operating time: Approx. 12 hours
Recharge time: Approx. 6.5 hours via USB or base station
Memory: 512K (over 5000 scans)
Dimensions: Scanner: 175 (L) x 72 (B) x 100 (H), Base: 200 (L) x 90 (B) x 51 (H) mm
Weight: 210g (Scanner), 230g (Base)

1D, 2D barcode reader
Wireless 2.4GHz (RF dongle) or USB-A for USB-B cable
Reading distance: 10-500mm
Operating time: Approx. 16 hours
Recharge time: Approx. 6.5 hours via USB-B
Memory: 512K (over 5000 barcodes)
Dimensions: 150mm (L) x 70mm (W) x 95mm (H)

125kHz RFID TAG
Designed as screw
plastic
9.5 mm Thread
12 mm head
19 mm long.
TAG is waterproof

RS232 Cable for Bargun Omni
Cable Length: 2Meter
DC Box located 20 cm from DB9 She connector.

125kHz EM 4xxx reader with USB
USB HID (plug and play)
Powered from USB
Additional purchases from Decimal to HEX, normal or reverse
Additions with start and or stop character
Supports: EC standard 125kHz
Dimensions: 100 x 65 x 23 mm
Material: ABS
REMEMBER: Order the desired version - additional purchase

RFID EM-Marin and QR code reader
125kHz EM4100/4200
Reading as facing right
Built-in buzzer for sound notification
Can read multiple formats
With CPU watchdog
Power supply: 12V DC
Wiegand 26/34 bits
Dimensions: 125 x 83 x 30 mm

module with eight relay output
5VDC from optically isolated digital input
GND, VCC, IN (digital input)
COM, NC, NO
Max load: AC 250V / 10A DC 30V / 10A - non inductive load!

MDB Male and Female
DEX Male and Female

Bluetooth RFID reader with WiFi incl. Holder and battery

Demo model!

Keyboard Emulation: 8 digits, 32bit HEX
Frequency: 13,56MHz Mifare Ultra Light
versions: Mifare S50, S70, ISO15693, ISO14443A / B
UID in positive Normal sequence
Power supply: 5VDC from USB port
Operating temperature: -10 - + 75 ° C
Reading distance: 5 ~ 15 cm
Cable length: Solved USB cable
Dimension: 118 (L) x 75 (W) x 17 ( H) mm
Weight: 250g ± 10%
desktop - table model

Dual band RFID TAG card
2.45GHz and 13.56MHz Mifare read/write
Programmable parameter
Dimensions: 86W x 54H x 6D (mm)
Weight: 25.8g
Combine active and passive RFID
Long operating time on battery
Wireless TAG programming
Supplied without battery (2 x 2032)

Long Range 2.45GHz RFID reads and writes for 140 m Range
Programmable parameter
1 x RJ45 (10/100 Mbit)
1 x RS232 (RX, TX)
1 x RS485 2-wire Protocol: ICMP, ARP, IP, TCP (Server / Client), UDP, DHCP, HTTP
Supply voltage: 7 - 15 VDC / 4 Watt
Dimensions: 107W x 138h x 30D (mm)
Weight: 222g
easy installation

Trigger to open cash drawers with Epson, Citizen or Star interface

To track 1, 2 and 3
Connects via PS2 port
Software not required
data will be inserted where the cursor is (HID)
Sound, reading speed, line breaks and æ, ø and å can set
Weight: 200g
Dimensions: 100 x 34 x 28
cable length: 2 meters
supply voltage: 5VDC (from PC)

Reader/Writing Tracks 1, 2 and 3
Standards IBM, ISO, ANSI, DIN
USB With Emulation of COM Port
Dimensions 65mm × 215mm × 58mm
Supports only ASCII (no special signs)
Supported with 24VDC 2.2A power supply

ST STM32 32-bit CPU with 512K Program flash RAM
2M Byte SRAM (1MB lookup table), 4M Bytes Flash RAM (For Font)
1 MB or 35,000 records Seite 128 x 128 dots graphic FSTN LCD display with blue backlight
Dual Color (Red / Green) LED Indicator
RS232 and USB virtual RS232 Seite 120 ~ 80 scans per second
Rechargeable Lithium Battery Pack (1700 mAh / 3.7V)
3.0V, 18mAh, MaxeII ML, Rechargeable Lithium battery for SRAM
Operating hours: Up to 24 hours and 28,000 scans
Certifications: FCC / CE / WEEE / RoHS
Weight: 175g
dimensions: 145 x 64 x 31
Operating Temperature: 0 ° C ~ 45 ° C
OS Support: Windows-based (98 / Me / 2000 / XP / Vista / Win 7 / Win 10)

Network RFID reader
10 / 100Mbit Ethernet interface
Supports MDI / MDIX
1 x RJ45 and 1 x DC connector
TCP Server, UDP, DHCP
for 13.56MHz Mifare card
Supply: 5V DC PSU Max 300mA

10/100M Ethernet interface
TCP Server, UDP,  DHCP
Til 125Khz ID Kort
Forsyning: 5V DC PSU max 300MA

Comes with cable for USB.

MCR-BARCCD-K kan læse både magnetkort (spor 1 og 2) og stregkoder.

RS485 Command Controllet Ready / Read
Set to Read. Called to Transfer Take UID Code
10 digit Hex - (26 digits for PC)
2-wire RS485 Half-duplex.
125 kHz EM format.
12vdc 0.2a (MDFollows not)
Dimensions: 113.5 x 45.6 mm (L X B)

Multi 13.56 MHz Mifare Reader
RS232 Connection
5VDC (Power Jack 5.5 / 5.1mm) Not included
Cabinet: ABS, indoor IP65
Dim: 88 x 56 x 18 mm

MDB Master / Slave Controller via USB
Simple API for integration
can function as VMC or payment terminal
USB-COM Port ACM Driver
Built-in relay, can be controlled via command
Power supply via USB or MDB
Does not provide power output on the MDB port
Technical demanding product - Support for setup / integration can be purchased

Honeywell 1902GER-2 Barcode Scanner
KUN stregkodelæser, uden ladestation
1800 mAh Li-ion minimum batteri
Op til 50,000 scanninger pr. Opladning
Trådløs

Genopladeligt Li-ion batteri, 3,7V, 1620mAh

IC / RFID / MAGNET motor reader
USB interface
three in one card reader
example. kiosks and the like
Automatic in / out

Zebra 8000T Z-ENDURE

Farvebånd til 200 kort (til PRINT-ID/PRINT-ID-MAG)

Evolis R3011 color ribbon

Paper- Printer Accessories - Thermal

Seiko Instruments RP-E11-K3FJ1-E-C5, POS, Termisk, 350 mm/sek., 8,3 cm, 5,8 cm

2.4GHz RFID reader with up to 200 meters
Omni-directional (SMA)
RS232, 10 / 100M Ethernet interface
Optional: GPRS or WIFI
Optional: 2 channel relay, 2 channel trigger input
Development kit (C ++, C #)
Compatible with active and passive tags
0-100m radius (depends on power output)
can identify 300 tags time-consuming
IP65
DC 5V power supply, 300mW
dimensions: 190mm × 120mm × 40mm without antenna
Dimensions: 320mm × 226mm × 133mm with antenna
Weight: 2 KG
Operating temperature: -40 ℃ ~ + 60 ℃
API interface for fast integration with existing software

125kHz RFID TAG
For Keyring
Waterproof
Durable
Gray
Dimensions: 40 x 30 x 7 (L x W x D)

Tilsluttes RS232 (serieporten)

S/H bånd til 1000 kort (til PRINT-ID/PRINT-ID-MAG)

Evolis R2011

Kan printe QR koder