insertion, avoiding power blackouts at the cable company or at any intermediate amplifying station and simply avoiding anything else the cable company can do to mess up your signal. In that respect, satellite is more reliable.

Disadvantages include lack of convenient portability, sensitivity to meteorological conditions, local zoning ordinances, and condo restrictions. Heavy storms can cause the receiver to unlock off the carrier frequency causing data loss. Likewise, snowstorms can unlock the signal by building up snow on the dish. Also sunspots can cause blackouts. Twice a year, geostationary satellite transmissions are affected by the suns energy due to their relative position between the earth and sun. This will affect receiver locations at various times of the day for 10 to 15 minutes, depending on your position on earth relative to the satellite.

Remember that a satellite operates in line of sight, and if there are mountains, buildings, or trees in the way (blocking line of site), it can be a problem, especially in northern latitudes. Lots of tinkering may be needed to align your dish to the satellite. You may even need to hire an installer to do it properly.

Questions to Ask

Is your latitude too high for direct line of sight?

Does it rain, thunderstorm, and snow a lot in your area? If so, you may want to consider a bigger dish or cable.

If reception is not strong enough, does the vendor have a bigger dish or a better amplifier? If so and you need to upgrade, what additional costs would you incur?

Internet Transmission

The newest development in data transmission is through the Internet. Advantages include portability and not needing to rent or buy a signal receiver box or satellite dish. You plug in wherever you are, in the office, at home, or on a trip.

Vendors offer real-time, delayed, EOD, or some combination on the WWW. Some require special software while others are pretty much open to universal servers.

As for speed, using Netscape and a 56 kbps modem through a local Internet service provider (ISP), one user reported his Internet feed was delivering data earlier than his cable feed! Another user reported data via the Internet arrives about the same time as data from S&P Comstock. On the other hand, one user said his Internet feed was behind cable all day on DJII, SPX, and NASDAQ. As cable speeds up to 56KB, this speed advantage of WWW over cable will likely disappear.

Disadvantages using an Internet feed include unreliable delivery rates because the Internets throughput rate is so unpredictable one minute to the next. Reported one user:

Once when we pinged the connection, our test revealed that the signal was required to traverse 28 Internet hops before reaching my computer. Other tests have

been as low as 7 and as high as 35. Each "hop" is another trip through a computer or router somewhere which takes time and is subject to [inducing additional] error.

Although Internet Services Digital Network (ISDN) lines make Internet communication faster than conventional lines, they are not much more reliable. You may not even be able to connect during very heavy trading, the time when you most need to.

You could also get disconnected abruptly from the WWW site if it is extremely busy. Your ISP may also have input/output (I/O) problems now and then. For example, incoming junk mail can be so voluminous that data processing at an ISP can temporarily grind to a halt, and during this time you will not receive any data.

Internet services fall into three categories whereby,

• Data is processed by a Java enabled Browser.

• Data is processed by a general purpose commercial application (e.g., MS Excel, Visual Basic, Delphi) that supports connection to the Internet.

• Data is processed by a custom stand-alone application that connects to the Internet, that in turn can pass data on to general-purpose commercial applications. Townsend Analytics is one such application. It connects to www.spcomstock.com, www.pcquote.com, www.intersat.com, www.marketconnect.de. If you want to use your own software, consider www.interquote.com, or www.naq.com.

Questions to Ask

Does the vendor offer real-time, delayed, or EOD?

Any special software required to process data from the Internet?

Data Reception

The third stage in the life cycle of a price quote is its processing at the receiving site. Signal Translation

At the receiving end of FM, cable or satellite transmission, the signal passes through a receiver (black box) undergoing several transformations before entering into your computer. First the signal is demodulated, which extracts relevant data from the analog signal and converts it to a digital data stream.

Next, it is sent to a microprocessor and the processing performed on this data stream depends on the microprocessors software. For example, DBCs receivers are driven by software called the Receiver Operating System (ROS), which is uploaded into the microprocessors RAM type memory by a small program in the users computer. Each of DBCs two data streams uses a fundamentally different ROS, each with advantages and disadvantages. In both cases, DBCs data dispatch center transmits all

information (price quotes, news, etc.) in binary (compressed) format. The ROS selects (prefilters) only the type of information the user has paid to receive. Now here is where the two versions differ:

1. DBC Signal. The ROS converts the prefdtered information into ASCII text format and then relays to the computer only the price quotes whose symbols are in the users portfolio. When only these data packets are sent to the users computer, the computers processing workload is fairly light. This version of the ROS also saves the most recently received price quotes for all the symbols in a portfolio in the microprocessors RAM, so the server can request them and have current prices whenever it is restarted. A good backup feature.

2. DBC BMI. The ROS relays to the computer all the prefiltered information, still in binary format. This makes the computers workload very high. This version of the ROS does not save specific prices in the microprocessors RAM and so the backup feature is missing.

Dumping all the markets data to your computer can create a very large workload. Data would include every tick of every contract month of every ticker of every subscribed exchange as well as all the options from your subscribed exchanges. Plus, it would include all the freebie indices and there are quite a few of them.

The bottom line here is that if the receiver is designed to send everything straight to your computer, charting and analysis performance will be heavily dependent on the speed and power of your computer. In this case, the easiest way is to get the fastest computer you can afford. A more serious procedure is to buy a second computer, whose sole purpose is to filter out all the quotes you are not interested in, then convert the remaining data to ASCII text and send it to the computer running your charting and analysis software. Dont laugh. I know several traders doing this.

Questions to Ask

Can the receiver prefilter for symbols exclusively in your portfolio?

Does the receiver send data to your computer in text or binary format?

Does the vendor have a developers kit that explains the format of the data

stream?

Time Clocks

Trading systems and related analysis rely heavily on the time associated with the trades being analyzed. As such, it is common (and necessary) for each trade to be time-stamped with a notation of the time at which the trade was consummated. Some data providers deliver the time of the trade along with the trade report, which consumes considerable bandwidth in the datafeed. Most, however, rely on the users software and computer to record the timestamp with the trade. Considering that a trade can be