A call auction is where market participants have the opportunity to place orders to buy or sell at specific bid or ask prices, which are then batched together and matched at predetermined time intervals. The purpose is to let market participants place orders at their acceptable bid or ask prices before a new token becomes available on the exchange order book, and before the Open Prices for new trading pairs are generated. The trading processing system determines a benchmark price (or an Open Price) by prioritizing orders using bid/ask prices and time of placements, while meeting the following three conditions:

1. Maximization of trading volume.

2. Successful execution of all buy orders priced above the benchmark and sell orders priced below the benchmark (deal closed).

3. Successful execution of either buy orders or sell orders that are priced at benchmark (deal closed). 

The aforementioned benchmark price will be determined as the Call Price and displayed to all. In a call auction, the process of generating a Call Price is completely automated. This process and price are known as Call Auction and Call Price, respectively.

Call Auction on HTX comprises two sessions:

1. Session I: Both placement and cancellation are allowed.

2. Session II: Only placement is allowed. Cancellation is not allowed.