A Call Ratio Vertical Spread is long one ITM call option and short two OTM call options.
The Max Loss is uncapped on the upside and limited on the downside.
The Max Gain is limited to the difference between the two strikes less the net premium paid.
When to use: When you are bearish on volatility and neutral on market direction.
Even though a Call Ratio Vertical Spread is the reverse of a Call Backspread, it is generally not referred to as being short a Call Backspread as a Call Ratio Spread requires up front payment and is hence a long strategy.
You will notice that it is very similar to a Short Strangle except the risk is limited on the downside.