Yes Transfer eq is only subject to approval. That generally means the inspector can determine if it is suitable for the use you employ.
I'm sure that the switch (double pole) George indicated is feeding a load center which provides adaquate over current protection upon transfer. (That would be a concern to all of us). Or I suppose that a DPDT switch for one circut that is protected by breaker on the generator is OK also.
All these situations are subject to conditions of installation.
I personall use a Gen Tran it allows individaul switching of each branch circuit and includes a flanged outlet for the portable connection of the supply cord.