---
title: tb
framework: cryptotokenkit
role: symbol
role_heading: Instance Property
path: cryptotokenkit/tksmartcardatr/interfacegroup/tb
---

# tb

The TB interface byte of ATR group, or nil if TB is not present.

## Declaration

```swift
var tb: NSNumber? { get }
```

## See Also

### Accessing Interface Group Protocol and Bytes

- [protocol](cryptotokenkit/tksmartcardatr/interfacegroup/protocol.md)
- [ta](cryptotokenkit/tksmartcardatr/interfacegroup/ta.md)
- [tc](cryptotokenkit/tksmartcardatr/interfacegroup/tc.md)