# Teller Interfaces

The Teller contract handles all interactions with end users and manages tokens issued to represent bond positions. Users purchase bonds by depositing Quote Tokens and receive a Bond Token (token type is implementation-specific) that represents their payout and the designated expiry. Once a bond vests, users can redeem their Bond Tokens for the underlying Payout Token. A Teller requires one or more Auctioneer contracts to be deployed to provide markets for users to purchase bonds from.

### Teller Interface

The [Teller Interface](https://github.com/Bond-Protocol/bond-contracts/blob/master/src/interfaces/IBondTeller.sol) defines the functions that all Teller contracts should implement. 

Significant functionality is left to specific implementations. 

The two Tellers implemented here both tokenize the bond positions, but this is not required. The functions Tellers must implement are:

```solidity
purchase
getFee
setProtocolFee // onlyGuardian
setReferrerFee
claimFees
```

### Fixed-Term Teller Interface

The [Fixed-Term Teller Interface](https://github.com/Bond-Protocol/bond-contracts/blob/master/src/interfaces/IBondFixedTermTeller.sol) defines the functions that should be implemented to tokenize and redeem fixed-term bond positions using ERC1155 tokens. 

The required functions are:

```solidity
deploy
create
redeem
batchRedeem
getTokenId
getTokenNameAndSymbol
```

### Fixed-Expiry Teller Interface

The [Fixed-Expiry Teller Interface](https://github.com/Bond-Protocol/bond-contracts/blob/master/src/interfaces/IBondFixedExpiryTeller.sol) defines the functions that should be implemented to tokenize and redeem fixed-maturity bond positions using ERC20 tokens. The required functions are:

```solidity
deploy
create
redeem
getBondTokenForMarket
```

The `deploy, create` and `redeem` functions are similar across each Teller that tokenizes bond positions but they differ in the arguments required and the type of token they return.