This type of deposit combines multiple accounts in different currencies under a single agreement. The depositor can convert funds between them, usually without terminating the contract or losing accrued interest.
The rate for each portion corresponds to the currency of placement: higher for domestic currency, lower for foreign currency. The overall result depends on both rates and exchange rate movements, as well as the spread between buy and sell rates for each conversion.
The primary purpose is to reduce currency risk through diversification, not to profit from exchange rate movements. Frequent conversions between currencies usually result in losses due to spreads, even if the direction is predicted correctly.
A reasonable approach is to determine the proportion based on the currency of future expenses and maintain it, using conversions only to restore the proportion rather than attempt to predict rates. The same result can be achieved with several separate deposits, so comparison should be based on overall terms rather than convenience.