33.74 is not used often. It is basically a backup frequency if 33.90 is busy with multiple calls. It is also used a lot for service calls (tree down, water emergencies ect.) Other times I've heard it being used is with major fires, they'll use it as a staging frequency. Also as far Griswold ambulance goes, they get dispatched on 33.80 and then directed to 33.88 or 33.90 or 460.000, depending on the type of call.