Systems and Subsystems

We are so used to having things work for us that we rarely take the time to understand how they work. In today's society, we take for granted just how complex are, especially the "simple" things that technology has made so easy. The whole reason for this is we don't think about the process by which the simple task is done. Since all we have to do is push a button we don't realize the sequence of all the steps that has to happen for the task to work.

Take a cell phone call, for instance. We push a button or two on the cell phone from our call list to call our best friend.

• First, of course we had to store that number in the call list.
• Once we push that button the phone checks the call list file.
• The processor chip in the phone then sends a series of instructions to the modem in the phone.
• The modem sends out pulses of radio waves to the local cell tower.
• The cell tower relays the waves to other towers or even a satellite.
• Another tower relays the waves to that person's phone.
• The modem in that person's phone picks up the wave pattern that it recognizes as its identity pulse. Then it sends a signal that there is an incoming call to the phone processor chip.
• The processor chip compares the identity of the incoming call to your known call list and sends a signal to their speaker.
• The speaker plays the ringtone that they have assigned to your number.
• They open their phone and respond "Hello"
• The microphone in their phone picks up the vibrations in the air from them speaking and changes them into electronic pulses. and sends them to the modem.
• The modem changes the electronic pulses to radio wave pulses and sends them to the cell tower or satellite.
• The satellite or tower relays them to the cell tower closest to you.
• The cell tower by you sends them to your phone modem.
• The phone modem converts the radio waves to electronic pulses.
• The processor sends the electronic pulses from the modem to the speaker.
• The speaker converts the electronic pulses into air vibrations.
• Your ear picks up the air vibrations which your brain interprets as your friend's voice saying "Hello"
• etc., etc., etc.,,

The list above is the PROCESS by which you have a phone call.

The INPUT was 1) energy from the batteries in the phones, from the power supply for the towers and satellite, from your body to push the numbers, and your friends body; also 2) input were the codes for your friend' phone number, the call list, the ring tone, and the conversion codes that change air vibrations to electronic pulses, electronic pulses to radio waves, etc; and 3)your friend's voice. In otherwords, everything that had to be preset for it to work, the energy for each step of the process, and the actual raw material (finger taps) that starts the process.

The OUTPUT was 1) the conversation, 2) heat from the energy use, 3)radio waves that didn't connect with the phones (they go out in all directions).

Cell phone conversations are Closed Loop Processes because there are machines that MONITOR the electronic pulses for quality and signal strength in each phone and machines in the towers that monitor the radio signals, plus you and your friend who recognize "bad" phone calls and turn off the phone till later.

This week you have been going over systems and their parts. This is to try to help you understand how things work together so that next week when we start building systems you have a better idea of how to start. What problems have you had this week? I know you have struggled with these ideas.