The first decision you need to make on choosing an outdoor intercom is whether you want a wired or wireless solution. A wireless system has the advantage of ease of installation, but there is always a possibility of interference. You seldom have to worry about interference with a wired system, but there's the expense of installing the wire. Both types of outdoor intercoms will be discussed here.
Wired Outdoor Intercom
Just like it sounds, a wired outdoor intercom has wires running between the outdoor speaker and the indoor units it is connected to. Usually the cable used is a two-conductor, shielded wire, but could be a computer network type CAT-5 cable depending on the type of intercom system. The shield on the two-conductor wire helps the wire resist picking up electrical interference from other electrical devices that could produce a buzz or hum on the intercom system. CAT-5 systems are usually digital devices so they do not have this problem.
The two-conductor systems are used for both commercial and residential properties. These systems generally comprise of two main components. The first is known as the "door station" and is fitted outside the entrance to the building The second component is called the "master station" and this is fitted inside the property. Depending upon the size and general layout of the property it may be more convenient or practical to have more than one master station.
The two-conductor systems are usually simple systems that allow communication between the outdoor door substation and a master station on the inside. If additional master stations are needed inside, then a multi-conductor cable with as many as 20 wires is run between the master stations.
With these systems, when a visitor arrives at the door they press a button on the door station and this triggers a short tone at the master station(s). Someone inside the property then answers this tone and the two parties are able to communicate with one another. The person at the door can communicate without pushing a button and the person at the master station has to push a button. An additional feature of these systems is a door release system which enables the door to be opened remotely by the person operating the master station.
While two-conductor systems require multi-cable wire between master stations, the CAT-5 systems use the same cable no matter how many stations are required on the inside, but these systems are typically more expensive to purchase.
Wireless Outdoor Intercom
When you need to communicate with people who are at an outdoor location and you can't run wires to that location, an outdoor wireless intercom is the solution. These outside wireless intercoms communicate to an inside station or portable handheld two way radio via radio waves. So wireless outdoor intercoms not only have the benefit of not requiring installation of cable, they also allow for mobility of the person or people monitoring the outdoor wireless intercom.
There are several varieties of these outdoor wireless intercoms available. You can get heavy duty, tamper resistant devices that communicate over long range, or lighter duty devices that communicate a few hundred feet. Some devices communicate using a proprietary method that only allows devices from the same manufacturer to talk to each other, while others are more open and allow mixing devices from different manufacturers. If you have existing two-way radios you use, you may be able to get outdoor wireless intercoms that talk to them.
One outdoor intercom system available is the Compact Wireless. This system will communicate with other devices in the MURS wireless intercom product line. It has a range of up to 1 mile, but with obstructions in between range will be less. These outdoor intercoms work in walkie talkie fashion where a button push is required to talk.
Outdoor Callbox Intercom
If you need a more heavy-duty outdoor intercom, then a wireless callbox like the MURS Callbox XT Outdoor Intercom may fit your application.
A callbox is a heavy duty, weather and vandal resistant wireless system that provides easy communication between the callbox at a specific fixed location, and a base station intercom or handheld two-way radio device. It allows for long range communication between the devices over a distance of up to one-mile. This distance can be increased with the addition of an external antenna. These systems have become very popular for businesses where reliable and easy to operate two-way communication must be available at all times.
Wireless callboxes use UHF and VHF frequencies to communicate. Some of the wireless frequencies require an FCC License, but there are five MURS radio frequencies that are unlicensed and very lightly used.
MURS stands for Multi-Use Radio Service. This is a newly created service for use in the United States and some Caribbean countries. It is a low power, short range service in the VHF (Very High Frequency) 150 MHz radio spectrum.
MURS radios have a power increase of four times that of the Family Radio System (FRS) radios that are so common. And unlike FRS, you can add a larger or external antenna to improve range. If you want to put an antenna on top of your building, you can do it with MURS. Some antenna manufacturers claim an external antenna can increase the effective radiated power of a transmitter by a factor of 4. Some MURS Radios can transmit up to four miles, and perhaps more with an external antenna.
If your application requires unlocking a gate or door from a remote location, then a callbox such as the MURS Callbox XT Outdoor Intercom with Gate Relay is what you need. This call box has a relay that can be controlled by pressing a button on a wireless intercom like the MURS Commercial Intercom or any two way radio with the 2-tone encode feature.
The MURS Callbox with Gate Relay also has a Sensor Input that allows it to also operate as a motion, gate entry, tamper or vehicle detection device. It will send a tone alert when optional switch/sensor status changes. The Callbox will send a warning tone when a change in the Sensor Input is detected. The Sensor Input will respond to an OPEN or CLOSED switch.
Choosing the right outdoor intercom for you depends on your application and your budget, but you can almost always find one that will work for you.
Author: David Onslow
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