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Public Cell Phones


This essay does not describe an existing computer program, just one that should exist. This essay is about a suggested student project in Java programming. This essay gives a rough overview of how it might work. I have no source, object, specifications, file layouts or anything else useful to implementing this project. Everything I have prepared to help you is right here.

This project outline is not like the artificial, tidy little problems you are spoon-fed in school, when all the facts you need are included, nothing extraneous is mentioned, the answer is fully specified, along with hints to nudge you toward a single expected canonical solution. This project is much more like the real world of messy problems where it is up to you to fully the define the end point, or a series of ever more difficult versions of this project and research the information yourself to solve them.

Everything I have to say to help you with this project is written below. I am not prepared to help you implement it; or give you any additional materials. I have too many other projects of my own.

Though I am a programmer by profession, I don’t do people’s homework for them. That just robs them of an education.

You have my full permission to implement this project in any way you please and to keep all the profits from your endeavour.

Please do not email me about this project without reading the disclaimer above.

Not everyone owns a cellphone and not everyone’s cellphone is working. The phone companies are removing all the coin-operated pay phones because of vandalism. This project is about a way of using a network of privately-owned cellphones as pay phones.

Yellow BlackBerry Curve

This is not strictly necessary, but ideally we would manufacture ruggedised, bright yellow cellphones. Why yellow? Because taxis are yellow and yellow is thus associated with public access. The colour yellow is not much used and is easy to spot, so is ideal for this purpose.

The cellphone should require a PIN (Personal Identification Number) to make a local call and a different PIN to make a long distance call. You might want to be able to disable this feature for private use. There is a app that tells you how much a long distance call of a given length will cost.

Yellow Tee shirt

We also make bright yellow Tee shirts that say Local call $2.

In the simplest case, you approach someone with such a phone, give them $2 (You would be free to haggle over price.), they key the local call PIN, hand you the phone and you make your call. Using such as cellphone would be even less complicated than using a coin-operated phone. All fancy features would be temporarily inhibited.

Without the PINs (Personal Identification Numbers), the phone is of no use, so there is not much point in a thief running off with it.

You might think, wouldn’t it be nice if you could insert a bank card or debit card to pay for the call? I can’t see any way to do that without inviting fraud. However, you could have a special phone card for paying that used a gas-tank approach. The company that issued such cards would take a cut. Fraud could net at most $20 or so, the contents of the gas tank. There are ways of making this fraud-proof but it requires putting quite a bit of intelligence and processing power in the card and giving them each unique private and public keys and the ability to detect valid digital signatures.

Free enterprise then would populate the world with public cellphones, when and where they were most needed. Stores could put one on the counter and offer it to clients. Otherwise, if customers use their land lines, they could lose business. People not officially in the pay phone business might also be willing to help you out in a pinch, once the protocol was understood and phones were designed so there was little risk to doing so.

You might think the cellphone companies would object. However, they would benefit. Frequent pay phone users would get their own phone and start making money too. They would already feel at home with the technology. The scheme creates a whole new low skill, low-investment business. Each one means a cellphone sale and contract for the cellphone company. The cellphone companies also benefit by having their products demonstrated and newest models featured.

Because it would be so easy for a customer to run off with a public cellphone, you have to make sure the cellphone has no value whatsoever to anyone but its legitimate owner. It should not allow the thief to make calls or go into business with it, even with some surgery on its innards. Ordinary cellphones are designed to encourage theft. This will turn out to be the trickiest part of the project since secure devices usually require special purpose hardware.

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