(1) Depository bank. As the issuer of ADR and the intermediary of ADR market, the deposit bank provides all necessary services for ADR investors.

(2) Custody bank. The custodian bank is a bank arranged by the depository bank of the issuing country of the basic securities, and is responsible for keeping the basic securities represented by ADR; Collect dividends or interest according to the instructions of the deposit bank for reinvestment or repatriation to the ADR issuing country, and provide local market information to the deposit bank.

(3) Depository trust companies. Refers to the central securities registration and settlement institution in the United States, which is responsible for the custody and liquidation of ADR.

Arbitrage can generally be divided into three categories: intertemporal arbitrage, cross-market arbitrage and cross-commodity arbitrage.

Intertemporal arbitrage is one of the most common arbitrage transactions. When the normal spread of the same commodity in different delivery months changes abnormally, the profit from hedging can be divided into two forms: bull spread and bear spread. For example, in the metal bull spread, the exchange buys metal contracts in the latest delivery month and sells metal contracts in the forward delivery month, hoping that the recent contract price will rise more than the forward contract price; Bear market arbitrage is the opposite, that is, selling the recent delivery monthly contract and buying the forward delivery monthly contract, expecting the price drop of the forward contract to be smaller than the recent contract.

Cross-market arbitrage is an arbitrage transaction between different exchanges. When the same futures commodity contract is traded in two or more exchanges, there is a certain price difference relationship between commodity contracts due to geographical differences between regions. For example, London Metal Exchange (LME) and Shanghai Futures Exchange (SHFE) both trade cathode copper futures, and the price difference between the two markets will exceed the normal range several times a year, which provides traders with opportunities for cross-market arbitrage. For example, when LME copper price is lower than SHFE, traders can buy LME copper contract and sell SHFE copper contract at the same time, and then hedge and close the trading contract after the price relationship between the two markets returns to normal, and vice versa. When doing cross-market arbitrage, we should pay attention to several factors that affect the spread of each market, such as freight, tariff and exchange rate.

Cross-commodity arbitrage refers to trading by using the price difference between two different but related commodities. These two commodities are substitutes for each other or restricted by the same supply and demand factors. The form of cross-commodity arbitrage is to buy and sell commodity futures contracts with the same delivery month but different varieties at the same time. For example, metals, agricultural products, metals and energy can all carry out arbitrage transactions.

The reason why traders carry out arbitrage trading is mainly because the risk of arbitrage is low. Arbitrage trading can provide some protection to avoid unexpected losses or losses caused by sharp price fluctuations, but the profitability of arbitrage is also smaller than that of direct trading. The main function of arbitrage is to help distorted market prices return to normal levels, and the other is to enhance market liquidity.

A simple example is borrowing money at a lower interest rate and borrowing money at a higher interest rate. Assuming there is no risk of default, this behavior is arbitrage. The most important thing here is the identity of time and the certainty that the income is positive.

In reality, there is usually a certain time sequence, or a small probability that losses may occur, but it is still called "arbitrage", mainly in a broad sense.

Generally speaking, arbitrage is the operation of buying low and selling high at the same time!

At present, in the securities market, there are ETF arbitrage, securities transfer arbitrage, convertible bond arbitrage and warrant arbitrage.