You've probably heard it more times than you can count: Warren Buffett, among others, emphasizes the investing notion of your "circle of competence." By that, of course, he means that when committing your rubles, you're better off when you stick to what you know. It's a concept that makes especially good sense when you're trying to establish defensive positions amid an unusually unpredictable market.  

With that in mind, I've spent more than a little time lately figuratively wandering along old trails, trying to retrace my own circles of competence. It's surprising that, as I survey the market and economic conditions, I continuously bump into one of my former favorites, cable industry leader Comcast (NASDAQ:CMCSA).

I've followed this Philadelphia-based company for nearly a decade, or since it served about 8 million cable subscribers -- a third of today's contingent. That was also before the company had rolled out its "triple play" offering of video, high-speed data, and telephone service.

But one thing that hasn't changed is the unusual managerial competence in place at the company. Quite simply, among all the corporations I've followed as an erstwhile analyst, I can't point to a single instance wherein a company -- regardless of industry -- could roll out a management group as capable as Comcast's CEO Brian Roberts and his team.

Oh, sure, the company will have some speed bumps to negotiate in the months and years ahead. While the triple play has pretty well dispatched across-the-board competition from satellite providers DirecTV (NYSE:DTV) and Dish Networks (NASDAQ:DISH), Comcast and its brethren, including Cablevision (NYSE:CVC) and Time Warner Cable (NYSE:TWC), will for some time feel heat at their backsides from telephone companies Verizon (NYSE:VZ) and AT&T (NYSE:T) and their own triple- (or occasionally quadruple-) play packages.

And, while it may be affected by the economy going forward -- especially in telephony, where lots of consumers are giving up their landlines and getting by purely with mobile -- Comcast nevertheless increased its profit by 38% in the most recent quarter. Beyond that, I'm betting that an increasing appreciation for digital video recorders and high-definition capabilities will serve to steadily expand Comcast's all-important average revenue per unit (ARPU) in future periods.

So, there you have it. Invest in what you know. From a long association with the company, I know Comcast. In this market climate, I'm more inclined than ever to urge my Foolish friends -- especially those interested in building defensive positions -- to spend time getting to know this king of cable. 

Comcast rates a pair of stars from Motley Fool CAPS players. Could your thumbs up push it to three?

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Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned. He does welcome your questions or comments. The Motley Fool has a well-known disclosure policy.