Here is another electrical block diagram of a typical 30AMP trailer.
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Look for something like this on the side of your trailer that houses a PULL OUT long heavy duty extension cord that will have a connection plug on its end that looks like these photos...
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Other trailer may have this as a separate 30AMP cable that you must attach to a plug on the side of the trailer that looks like this.
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The standard SHORE POWER 30AMP Male Connector that you plug into a camp ground pedestal looks like this.
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This will plug into a typical camp ground pedestal socket to provide your trailer 120VAC that looks like this
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Camp ground pedestals may also have connections for 30A and 50A cable connections.
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Hope some of this may help for what to look for on your trailer. the older trailers may be slightly different then the modern todays trailers. Trailer electrical system must follow safe electrical codes just like a house wiring does. All must be safe to use.
Using a double MALE connector sure doesn't sound like a safe thing to use for me.
Let everyone here know what you are finding so we can help more.
Roy ken