People love to eat out. How many times have you gone to a restaurant and had to wait for a table? It used to be that someone would take your name and then yell out or call over an intercom when your table was ready. Some restaurants still do this, but many now use restaurant pagers.
You've probably seen these devices. The pager is a small plastic box that the hostess hands to you when she takes your name. You are then free to roam about within the immediate vicinity of the restaurant. Eventually, the pager lights up or vibrates, signaling that your table is ready. You take the pager back to the hostess and are led to your table.
In this edition of HowStuffWorks, we will explore these pagers and how they work. You will learn about the master transmitter and see the simple technology that operates the pager itself. But first, let's examine the basics of paging.
What is a Pager?
A pager is a very simple radio that listens to just one station all of the time. A radio transmitter broadcasts signals over a specific frequency. All of the pagers for that particular network have a built-in receiver that is tuned to the same frequency broadcast from the transmitter. The pagers listen to the signal from the transmitter constantly as long as the pager is turned on.
Each pager has a specific identification sequence called a Channel Access Protocol (CAP) code. The pager listens for its unique CAP code. When it hears the code, it alerts the user and may provide additional information, depending on the pager type.
There are five basic pager types:
- Beeper - The first and simplest form of paging, beepers provide a basic alert to the user. They're called beepers because the original version made a beeping noise, but current pagers in this category vary in the type of alert. Some use audio signals, others light up and some vibrate. Many of them provide a combination of alerts. This is the category that the majority of restaurant pagers fall into.
- Voice/Tone - These pagers provide the ability to listen to a recorded voice message when you are alerted that you have a page.
- Numeric - These pagers provide the ability to send a numeric message, such as a phone number, along with the page alert.
- Alphanumeric - These pagers provide the ability to send a text message along with the page alert.
- Two-way - These pagers provide the ability to send as well as receive messages.
Regional and national paging networks set up towers, like those used for cell phones, to cover large areas. On-site paging systems like the ones used by restaurants use a small desktop transmitter. In the next section, we will take a closer look at this device.
The Master Transmitter
To operate the pagers used for on-site paging requires a master transmitter. The master transmitter sends out the signal that the pagers are listening to. A good analogy is to consider the master transmitter as a radio station and the pagers as radios tuned into that station.
The actual frequency used by the master transmitter varies between various models and manufacturers. Their coverage area can range from a few hundred feet to several miles, depending on the power of the transmitter. To page a customer, the hostess enters the numeric code for that pager into the master transmitter. The hostess may also select a specific option, such as the code for "table is ready" or the code for "lost pager."
Most master transmitters display the last several pagers contacted. Some systems can handle up to 10,000 individual pagers, much more than any restaurant should ever need! A popular option is to connect the master transmitter into the telephone system of the restaurant. This allows a hostess or other member of the restaurant staff to initiate a page from any phone in the system.
The pagers typically run on rechargeable batteries. A recharging station is used to recharge the pagers easily. For example, the JTECH pagers in the image above have a set of metal contacts on the bottom of each pager. These contacts are connected by screws to metal plates on the pager's circuit board. The metal plates lead to the battery pack. Also, the screws thread into exposed metal balls on top of the pager. These metal balls touch the metal contacts on the bottom of the pager stacked on top of that one. This passes power through to that pager, which then passes it on to the next and so on.
Inside a Restaurant Pager
Inside a typical restaurant pager is a very simple circuit board with just a few basic components:
A simple radio antenna, made from a coil of wire wrapped around a metal core, picks up the signal from the master transmitter. This signal is sent to the microprocessor, where it is compared against the CAP code for that pager. When the signal matches the CAP code, the pager alerts the user using one or more of three methods: audio, visual or vibratory.
An audio alert usually plays a tone or series of tones through a tiny piezoelectric speaker mounted directly on the circuit board of the pager. Some pagers actually play a prerecorded voice alert, such as "Your table is ready." In many pagers, a series of LEDs flash rapidly or simply light up when an alert is sent.
As for the pagers that vibrate when activated, inside is a small DC motor:
You can see that a small weight is attached to the motor. This weight is mounted off-center on the motor's spindle. When the motor spins the weight (at approximately 100 to 150 rpm), the off-center mounting causes a strong vibration.
There you have it. The next time you have to wait for a table at a restaurant and the hostess hands you a pager, you will have a whole new appreciation for the elegant yet simple technology that lets you wander while you wait.