It can be hazardous for the do-it-yourselfer to be standing on a ladder to cut high branches with a saw. Instead, keep your 2 feet planted firmly on the ground, and use one of the tree pruning tools listed below. I also discuss a hedger built "on a pole," meant for trimming tall hedges. The tree pruning tools, proper, that I cover below are diverse in nature. One link is for ropeless pole pruners, specifically, while another points to a more generic treatment of pole pruners (namely, a variety of fiberglass, telescoping models). A third link concerns pole chain saws, useful for cutting larger limbs.
With "Hook-N-Pull" ropeless pole pruners, just place the hook sitting at the end of the fiberglass pole over the branch to be cut, then pull the sliding shaft. Pulling the sliding shaft engages the cutting blade. After the cut, a spring efficiently retracts the blade back to its starting position.
Some pole pruners give you the reach you need for trimming via a telescoping pole. This review looks at fiberglass pole tree pruners. For the Corona brand, the telescoping action is controlled by a nut; the mechanism may vary slightly for other brands of pole pruners.
Treat pole chainsaws as specialized tools for your tree pruning needs: use them to prune medium-sized branches. This Black & Decker model cuts through bare wood (up to 6") just fine. The only question is: Do you have sufficient need for trimming such branches to warrant buying a specialized tool? Many may prefer the wider usage they'll get out of tools such as items #1 and #2 above. But if you live on a wooded property, for instance, you might fall in love with pole chainsaws!
These hedgers are something of a cross between pole pruners and conventional hedge trimmers. Their blades definitely say, "hedge trimmers," but their length and telescoping action call to mind pole pruners. This model has a cute name that suggests its function. Called the "Remington Axcess Trimmer," it's meant to give you "access" to the tops of tall shrubs, so you can "give them the ax."