Pager Major

by Danny Burstein

This article has been put together to answer some of the more common questions about pager systems.  It is primarily focused on the U.S. and Canadian arrangements, but other countries are not forgotten.

What Is a Pager Anyway?

As usually described, a pager is a portable unit, generally about half the size of an audio cassette box, which can be signaled to send a one way message to the pager owner.  (There are lots of versions available.  For example, Motorola offers up the Sensar which is shaped like a flattened-out pencil.  There are also extra thin credit card units, PCMCIA cards that fit into computers, etc.)

What Types of Messages?

The earliest units, usually called beepers, simply gave a tone alert.  This was a signal to the wearer to, for example, call the answering service.

The next step was units which could display numbers.  While the most common use is to send it the phone number you want the person to call, you can, of course, add code numbers to mean anything else you'd want.

For example, the number XXX-YYYY-1 might mean to call the XXX-YYYY number at your leisure.  XXX-YYYY-9 might mean call ASAP.

The most recent units, called alphanumerics, display complete written messages.  So, for example, the pager could show the message: "Please call home, you have a letter from the IRS."

There are also voice pagers which will let you actually speak into the phone and have it come out the person's pager.  These are pretty rare.  Typically these are used within local areas, i.e., in a factory.  They are also used, on occasion, by groups such as volunteer fire departments.

How Are Messages Sent to the Pager?

Messages are sent by radio.  Actually, it's a bit more complicated than that.

Let's take a look at how a pager actually works: The pager is a small sized radio receiver which constantly monitors a specific radio frequency dedicated to pager use.  It remains silent until it "hears" a specific ID string which tells it to, in effect, turn on, and then listen up for, and display, the forthcoming message.  (Again that could be a numeric or other string.)  This ID is called (in the U.S.) a CAP code (Channel Access Protocol code).  It has nothing to do with the phone number you call or the ID you give to the page operator (see below).  (The ID number you associate with the pager is actually merely "column a" of a lookup table.  The pager radio service uses it to get the CAP code, which is in "Table B," and sends the CAP code over the air.  These tables can and are modified each time a new pager is added to the database.)

So the key point is that the pager company radio transmitter is constantly sending out pages, and your specific unit will only activate when it hears its ID/CAP code over the air.

How Do I Send Out the Message?

This depends on your pager vendor.  Let's take the most common examples:

Alert Tone Only (The Old Style):  You call up a phone number assigned to the pager.  You'll hear some ringing, then a signal tone.  At that point you hang up.  Shortly afterwards the pager transmitter will send out the individual unit's CAP code and it will go off.  (Note that earlier models, some of which are still in practice with the voice pagers, don't use a CAP code but instead use a simple tone sequence.  Since these give a very limited number of choices, they are pretty much phased out except, again, for things like volunteer fire departments.)

Touch-Tone Entry:  You will call a unique phone number dedicated to the specific pager.  It will ring, then you'll hear a signal tone.  At that point you punch in, using Touch-Tone, the number you want displayed on the pager.  A few seconds later the transmitter will kick out the pager's CAP code, followed by the numbers you punched in.  Then the pager will give its annoying alert tone, the person will read it, and call you back.  (Note that there is a variation on this in which the company uses a single dial-up phone number.  You call it up, then punch in the pager's ID number, and continue as above.  This is often used by nation-wide services with an 800 number.)

Alphanumeric:  With this one there are various ways of getting the message to the system.

Via an Operator:  The pager company will have you dial-up their operator.  When they answer, you give them the pager ID number and the message.  They'll type it into the computer and shortly afterwards the transmitter will send out the CAP code and the message.

Using Your Computer:  Most pager companies with alphanumeric have a dial-up number you can call yourself.  Some of these will work with regular comm programs, while others require proprietary software.  If you call the tech department chances are they will give it to you.  (They'd rather have your computer call their computer than have you call a person.)  The most common method is to have your computer dial-up the number, then you type in the pager ID, followed by the message.  Again, a moment later, the system will transmit it over the air, etc.  (There are also various software packages that automate some of this.)

Special Terminals:  Because of the popularity of this type of system, there are various stand-alone terminals specifically designed for this purpose.  The most common one is the Motorola AlphaMate and it's pre-programmed with many of the functions.  It's basically a half-decent keyboard with a two-line display, and is set up with the phone number of the company, etc.

How Large/Long a Message Can I Send?

This depends on a few key items.  This is of most concern with an alphanumeric, although it has some relevance with numeric ones (i.e., if you're giving a long distance number, extension, and code...).  In no particular order these are:

The design of your sending computer or pre-programmed terminal:  For example, if you get an AlphaMate, chances are it will be preset to 80 characters.  (You can reset it, provided the next two items work out).

The design of the pager transmitter system:  It will place a limit on the maximum length message it will send over the air.  This can vary dramatically.  Generally (with a big YMMV) you'll get at least 15 numbers with a numeric, and at least 80 characters on an alphanumeric.  Some systems will allow up to 225 or so alpha characters.

The design of the pager:  Especially a problem with alphanumerics.  Many of the ones on the market will only hold 80 characters so anything above that will be lost.

My Company Has Given Us Pagers, and I Notice That I Have Both an Individual ID and a "Group" Number.  When We Page Out to the Group, Everyone's Unit Goes Off.  How Does This Work?

Remember that a pager is basically a radio receiver that is constantly monitoring for its CAP code.  You can get pagers which listen for more than one.  In this case (which is quite common) your personal CAP code might be YYYY, while your boss's might be YYZZ.  In addition, both pagers will be listening for the CAP code ZZZZ.  When ZZZZ is detected, all the pagers with that CAP code will go off.  (Alternatively the pager company's computer may be smart enough to take a group ID and translate it into CAP codes XXYY, XXYA, XXZZ, etc., and send out fifty sequential messages.  There are some software tricks that reduce overhead here so it doesn't actually send the same message 50 times.)

I Keep Hearing About Sports or News Services Available by Pager.  How Do They Work?

Keep in mind that pagers work by constantly monitoring the radio channel for their CAP code.  So if you have ten pagers, or a hundred, or a thousand, all with the same CAP code, they will all go off at the same time.

The service company will have someone (or perhaps, a smart computer) monitor the news broadcasts/radio channels for something interesting.  At that point they'll send out the message to the group ID/CAP code subscribing to that information.  This way the news company sends out one message and it gets displayed by all subscribers.  (Again, they can also send out the CAP codes for the 500 subscribers.  It gets into a security/cost/radio time equation as to which method they'll use.)

So if I Find One of These Sports-News Pagers on the Sidewalk I Can Use It for Free?

Umm, kind of.  As long as the company providing the service keeps using the same group code, your pager will continue to receive the messages.  But the individual pager ID will probably be changed immediately so you won't be able to use it for your personal messages.  Note also that some pagers do have the ability to be turned into a lump of clay over the air.  Very few systems have actually implemented this security feature (which is called "over the air" shutoff), but it is there.

I've Found a Pager on the Sidewalk and Would Like to Use It.  What Can I Do?

Not much.  Keep in mind that you need an account with the paging company for them to send out the radio signal.  So unless you keep paying them, the pager will soon be a paperweight.  You might as well turn it in for the reward...  (On the other hand, if you already have a pager, you may be able to get this new one cloned to your first one, which will allow you to have a duplicate unit.  See below.)

Speaking of That Pager on the Street, It's Got All Sort of Numbers on It.  What Do They Mean?

There will be a lot of items printed, some by the manufacturer, some by the dealer.  In no particular order these will include (usually in very small print):

  • The pager's frequency.
  • The pager's serial number.
  • The CAP code programmed into it.

Very frequently, especially with numeric units, there will also be the phone number assigned to it.  And, of course, there will be the dealer's name, the local supplier, an "If found here's the reward number," and other housekeeping.  Note that often the CAP code will not be printed on the unit, but will only be readable via the programmer.

Can I Listen-In/Monitor Pager Channels?

Kind of.  The frequencies are readily known and the data is a digital stream going over the air.  There are various vendors of equipment to decode the material and display it or feed it into your computer.  Some of these folks advertise in communications magazines such as Popular Communications.  However:

The federales and the pager companies don't like you doing this (see the ECPA).

The volume of traffic is quite high.  If you figure a 1200 baud channel in use 75 percent of the time, well, you can work out the math.

By the way, the numeric units do not use Touch-Tone over the air.  Some did way back when, but I doubt any do these days.

I Have a Pager for Which I'm Paying Big Bucks Every Month.  I Miss a Lot of Pages Since I'm in the Subway a Lot.  What Can I Do About This?

There are several things:

Some of the pager companies will re-send messages on request.  Basically, you call up their phone number, punch in a security code, then go through a menu which tells them to resend the last, say, five hours worth of messages.

You can get a second pager unit cloned identically to the first.  Leave this one at home or in your office.  When you get back you can compare its messages to the one on your belt.  While the message may be a few hours late, at least you'll be getting it.

Actually, most pager companies will refuse to clone your unit for you.  However, there are many third-parties which will do it.  Check out the ads in technical and communications magazines.

What Are the Prices and Services Offered?

These vary dramatically by area and company.  Unfortunately, there is no central database keeping records on this.  Generally the following factors get counted in determining what you'll be paying:

How sleazy the company is.

Which type of pager and service you get.  Again, the most common are numeric (cheaper) and alphanumeric (more expensive).

Level of usage.  You may get, say, 25 free messages a month and then pay $0.25 for each additional.

Whether you own the pager or lease it.

Insurance, etc.

Area of coverage.  Smaller area means less expensive.

Speaking of Coverage, What's This Satellite Nation-Wide Paging?

Well, it's not quite what they're telling you.  It's not a single satellite covering the nation.  Rather, what's done is: You call up the paging company.  It then signals transmitters in the top 500 cities to send out your CAP code.  Shortly afterwards you get the message.  Note that you are not receiving a satellite transmission.

What's in the Pipeline?

Two key features are slowly filtering down.

Much more pager memory/longer messages.  Most pagers are severely limited in the amount of material they can hold, with a typical maximum being about 20 messages.  Units with much larger memories, or even better, units that are hooked into Palmtop or laptop computers, are making it to market.

Two-way communications.  In its simplest form this allows the pager to verify reception to the transmitter.  Also on the way is complete two-way communication which would basically be wireless email.  These systems are still a bit limited, but are rapidly gaining footholds in industry and should soon be consumer level.  Take a look, for example, at what the FedEx folk carry.

Updates and suggestions should be sent to dannyb@panix.com.

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