|When you need a way for clients, students, employees, or anyone else
to communicate with you from distant areas of your campus or property, a
callbox or call box is one way to do it. A call box is a box made of
metal or fiberglass that contains electronic circuitry that enables
someone to press a button or pick up a handset and call a central
location for assistance. Some callboxes also allow calling a portable
radio so that assistance can be mobile.
There are two main types of callbox units available, wired and
wireless. A wired callbox involves running a cable to it from the
central location. This guide is about the other kind, the wireless
The benefit of a wireless callbox is that you save money by not
having to do trenching and running expensive cable to the unit. You also
donít have to pay any air-time or telephone service fees with these
wireless systems. As mentioned, another benefit is that since the unit
is wireless, people monitoring the units can carry handheld radios that
communicate with the callbox. That allows your monitoring people to be
The range of these units is several miles, which can be extended by
adding an external antenna. Some units can use radio repeaters to extend
this range even more.
If you have existing two-way business radios, youíll want a system
that can integrate with them. Some callboxes can be programmed to be
compatible with virtually any brand of VHF or UHF business band radio.
You can get call boxes that require an FCC license, or you can get
units that are certified for use on special FCC License-Free MURS
Business Frequencies. If you choose a licensed version, the license is
usually not too difficult or expensive to obtain.
One problem you may have in placing a call box is the lack of
available power. Youíll want to choose a system that lets you use
battery or AC power. You can also get units that have optional solar
power so that they can run for several days on a single day of sunshine.
If you need to remotely control gates, magnetic door locks, or
barrier arms from your portable 2-way radio or desktop base station
intercom, then select a unit that has this capability. With this ability
you can let someone in a gate or door when they call you. There are
units that also let you turn on a strobe light at the callbox location
to help draw attention to it.
Another useful feature is the ability for call boxes to store a voice
message that is played when someone presses its button. This could be a
message that gives the caller specific instructions on what to do. These
units can also send a second and different voice message alert to the
monitoring central location or portable radios. This message could give
the callboxes location or it could be an emergency message of some type.
If you have several callboxes in use and you need to know the
location of the unit calling in, then you can get a call box that
transmits a unique numeric identifier to a radio that has the ability to
decode this identifier. This is like having a telephone with Caller ID
By adding a motion detector or some other detection device, you can
be alerted when that detection device is activated. Some callboxes will
send either a tone alert or a custom voice alert when the detection
sensor status changes. If this voice message is not immediately
answered, the alert message is resent multiple times.
If you are running your system on battery power, you need a unit that
has battery conservation mode. In this mode, only the absolute
necessities for operation are powered, and the unit can not accept calls
to it; it can only make calls. You can attach an external sensor to
automatically put the unit into full power mode when someone is detected
near the box. This will allow you to make a call to it.
Other useful features:
- If you want to listen to whatís happening around the call box,
then youíll need a unit that can be paged so you can use the callbox
microphone to monitor the sound around it.
- A low battery alert or external power fail tone is sent to the
monitoring portable radio or base intercom.
- A paging feature allows selective calling of individual boxes or
a group of callboxes simultaneously.
- The busy channel feature prevents someone from transmitting if
someone else is using the radio channel.
- Wireless callboxes have fast installation since no wiring is
- Entry keypad with built-in relay lets people enter a code at the
call box to open a gate or door. Remote opening of the gate by
monitoring personnel can still happen also.
These callboxes are being used for applications like parking lots,
college campuses, airports, hospitals, construction sites, manufacturing
facilities, resorts, hotels, farms, warehouses, delivery docks,
campgrounds, gated facilities, or anywhere people may need assistance.
So by using call boxes, you can put clear wireless voice communication
anywhere you need it, quickly, without expensive trenching and monthly
MURS Wireless Callbox units from IntercomsOnline.com can do most of
the features listed here.
Author: David Onslow