The purpose of the modem is to modulate and demodulate the electonic analog pulses of the computer to pulses the phone system can handle. Believe it or not, the first modems were the size of a small refrigerator. Not only were they large but strict regulations required that they only be moved and hooked up by phone company employees. And for many years modems could not be hooked directly to the phone company network. The first of many problems with early modems , other then their painfully slow 4,800 bps transmission rate, (Just how slow? Click here for a better understanding of speed.) was the fact that they were connected to the phone lines by a backwards little device called the acoustic coupler. This was a box that coonnected to the computer and the modem then a handset was laid on top of it. This would be the equivalent of sending your favorite song to your best friend from your stereo to a cell phone and then having them listen to it on a speaker phone. Also sounds in the room at either end could disrupt or distort the transmission. However, after deregulation of the phone company by the FCC, modems became cheaper and smaller due to increased competition. A modem has always been a gateway to a wealth of information in text form such as databases of information. Or as they were first use to wire complex math problems to a remote supercomputer. Modems have always been a valuable tool. However, with new high speed technology, the modem can transmit everything from the President's speech to your favorite sports stats.
Each port has a specific funtion. If you were to start at the port marked one and continue from left to right, the port uses would be as follow:
1. Protective Ground<------Drains minor jolts from the line.
2. Transmitted Data<-----Sends things from the computer to the Modem for transmision.
3. Recieved Data<----Sends data from the other domputer to yours.
4. Requested a Send<----Requests permision to send some data to the other computer.
5. Clear to Send<---when your computer gets the signal from the other computer's pin 4 it says "lay it on me" with this.
6. Data Set Ready<--when the connection has been established, this one says "we've got a connection"
7. Signal Ground/Common Return<-sends the equivalent of a carraige return <pressing return>
8. Received Line/Signal Detector<-detects carrier signal (dial tone)
9. Data Set Tester<-tests if everything is coming over the line ok
10. Data Set Tester<--ditto
11. Not Assigned<-an empty void of nothingness
12. Line Signal Detector<-checks the phone line's use
13. Secondary Clear to Send<--helps pin 5
14. Secondary Transmited Data<-port 2's helper
15. Transmision Signal Element Timing<-I'll admit it. This one's got me stumped
16. Secondary Received Data<-helps pin 3
17. Receiver Signal Element Timing<-Don't know
18. Unassigned<-Empty, Empty, Empty
19. Secondary Request to Send<-helps pin 4
20. Data Terminal Ready<-says "we're connected-alk away"
21. Signal Quality Detector<-determines how fast your modem can go by checking how much data is lost in transmision
22. Ring Indicator<-tells the computer the phone's ringing
23. Data Signal Rate Detector<-like a cop on the highway keeps everyone moving at a safe speed
24.Transmited Signal Element Timer<-no idea
25. Unassinged<-another unused pin, sheesh
Some of these pins are used all the time, while other are used only at certain times. It's these little pieces that really drive the modem. Just think. As you are viewing this page, these are clicking and clacking away and working very hard to keep your data flowing smoothly.