You're driving down the highway, engaged in an important business negotiation on your cell phone when your phone suddenly goes blank. "Uh oh! Did I blow the deal?" rushes through your panicked mind -- until you're able to reconnect with the other party, which hopefully is momentarily but might be much longer.

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Almost every cell phone user has a story like this one. It's a fact of cell phone life. While we think of cell phone networks as being complete -- that is, fully developed, a view made stronger when one looks at the vast coverage area maps provided by cell phone service providers -- the networks are really a work in progress.

Terrain, your location relative to the cell site or tower and interfering objects are the biggest factors that affect cell phone reception, according to Don Carretta, executive director of Verizon Wireless' Western Pennsylvania network.

To understand why, it helps to understand how cell phones work. Because they not only carry the call but also need to communicate with the cell site so the call gets routed properly, cell phones need to be a lot smarter than your standard landline telephone.

When you drive down the street with your cell phone on, it is constantly sending out radio signals, looking for all towers within range and determining which one is currently providing the best signal over which it can communicate.

It connects you with that cell site but continues to monitor for other neighboring cell sites. When your signal from the original cell site starts to dissipate, it already has the information it needs to find the next, best connection point and reconnects your call with the new site -- a process called a soft hand off.

In this way, the cell phone can allow you to move between coverage areas without losing the signal for a perceptible time. With so-called Code Division Multiple Access (CDMA) technology, used by Verizon, your phone can talk to three towers at one time, decreasing the likelihood that you'll lose your call.

Even with this advanced technology, you can lose a call frequently, no matter which cellular company sells you its service. That's because coverage is not 100 percent, even where the coverage maps indicate you have service.

In some cases, you may notice that your call gets dropped in a location that normally works fine.

That could be due to capacity constraints. Each cellular site can handle a certain amount of calls at the same time. Once it has reached its maximum capacity, the next call won't get handled. Different cell sites have different capacities depending on how much equipment the cellular service provider has placed in that location.

If the service provider finds that lots of calls are being dropped abnormally, it can choose to install additional capacity. The cell service providers are careful about where they add capacity because it could cost them several thousand dollars per site.

Sometimes, even having a cell site or tower near you doesn't mean you'll get good reception.

Take Mt. Lebanon Boulevard on the Castle Shannon/Mt. Lebanon border, a bustling area with homes, apartments, offices and shopping centers. Verizon has three cell sites within two miles of the boulevard -- at the top of the Cyclops building in uptown Mt. Lebanon, on the Holy Cross Greek Orthodox Church on a hill overlooking Gilkeson Road and at the Duquesne Light substation on Route 88 in Castle Shannon.

The closest is less than eight-tenths of a mile from Mt. Lebanon Boulevard, yet cell service in this area for Verizon practically disappears, while competing vendors T-Mobile and Sprint have adequate coverage to complete calls.

Verizon's Carretta says that in hilly Western Pennsylvania, the terrain becomes more of a factor than, say, in flat Phoenix, Ariz., and that low-lying areas such as this one on the Castle Shannon/Mt. Lebanon border are challenging to cover because the signals have problems reaching them.

There may be hills between the cell tower and the area in which the cell phone is located, thereby blocking the signal. Carretta said that if you're in a building, where you stand in the building also affects signal strength. Even the seasons affect cell phone reception, because leafy trees block more signal than bare trees, he said.

Another issue is signal strength. Making a clear phone call in a cellular area with a strong signal is easy for almost anybody. But if you're in areas with marginal or low signal strength, you may need to help your call along.

If you have a phone with a retractable antenna, raise the antenna. If not, consider changing to a phone with one. The stubby antennas don't work as well as raised antennas in marginal areas.

If you're inside, you'll generally get better reception if you stand near a window. If you're in a multistory building, you'll usually get better reception if you are on a floor near the top of the building.

While wooden structures don't pose too many problems for cell phones, concrete and metal structures block more of the signal, making it more difficult for your phone to communicate with the closest cell site. You may have to go outside.

In general, if you're in a low-lying area and simply must get service, go toward higher ground.

When all else fails, find out whether a competing cellular service provider has better service in that area.

It will differ from location to location, even between locations that are right next to each other. When you do make the change, you can have the new service move your existing telephone number along with your service change.