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content/notes/08-proximity sensors.md
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@ -85,7 +85,11 @@ Proximity Sensors & Near Field Communication 11
- Data exchange rate today up to 424 kilobits/s
- Usually used for Smartcards, digital payment, or device to device communication/ authentification NFC smartcards
Proximity Sensors & Near Field Communication 12 NFC-based communication / authentification
> [!INFO] small transmitters can be read with a large reader
> nfc is one specific spectrum of rfid
![Proximity Sensors & Near Field Communication 12 NFC-based communication / authentification ](https://i.imgur.com/WwidfDA.png)
> [!INFO] phones are a reader. but they can also emulate a tag
Proximity Sensors & Near Field Communication 13
- Each full NFC device can work in three modes:
@ -96,6 +100,8 @@ Proximity Sensors & Near Field Communication 13
- NFC peer-to-peer
- Enables two NFC-enabled devices to communicate with each other to exchange information in an adhoc fashion. 14
> [!INFO] Three modes. emulation, writer, p2p.
Proximity Sensors & Near Field Communication
- Different technologies for sensing proximity or exchanging data (often dual purpose)
- Stand-alone infrastructure approaches
@ -113,9 +119,12 @@ GPS - Overview
- Galileo (Europe, expected operational since 2020)
- Local coverage (DORIS, IRNSS, ..)
> [!INFO] initally only for millitary. now open to anyone but need under open sky
GPS - Applications
- Numerous GPS applications & GPS Receivers:
- Military
- initally for remote guided bombs
- Car navigation
- Marine
- Flight control
@ -135,6 +144,10 @@ GPS - History
- Accuracy errors of 100m
- SA was removed for civilian users in 2003.
- GPS achieved initial operational capability (24 Satellites) in 1993 GPS – Satellites
![original gps diagram](https://i.imgur.com/PJYIoMo.png)
GPS – Satellites
- Constellation of 24 + X satellites transmitting radio signals to users
- Altitude of 20,000km (approx.)
- Each satellite orbits Earth twice/day