December 2010

FM Wireless Power Line Intercom

A customer contacted us looking for a wireless intercom to connect between a downstairs and an upstairs room addition. They had a 3-channel intercom that communicated over the house wiring using FM frequencies. It used to worked fine except the few times when they plugged in a laptop nearby to charge.  Then they got nothing but static.  Then they purchased a high definition flat screen TV and the intercoms either had no communications at all or a lot of static.  They purchased another set of intercoms with the same results.

These intercoms are also known as Power Line Carrier (PLC) intercoms. PLC intercom systems communicate using a very low FM frequency over your house’s existing 110 volt AC house wiring that supplies power to receptacles and light fixtures. You just plug them in anywhere you have an outlet and they’re ready to go. Technically they are not wireless, but they are sold that way.

While they sound like the ideal solution for basic applications, most users are typically not happy with these intercom systems.

These units are very susceptible to interference from both inside and outside the house or business. You may experience buzzing, poor audio, or they may work perfectly well for you. Or as the customer above experienced, they may work well for you and then when you or your neighbor adds some new electrical device, they could quit working for you. You also could experience problems with units not being able to communicate because of the way your house wiring is done. The signal may not be able to cross to the second “phase” of your house wiring (220 Volts is run to each house and then split into two phases to give you 110 Volts). These intercoms are usually very inexpensive. These systems are not recommended for most people, but they are cheap.

A couple of the brands you’ll find in these intercoms is Westinghouse and Novi.

Due to their high return rate, you won’t find PLC intercoms on .

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Military use of MURS Radios

In some military applications, radios normally require a frequency clearance via a DD 1494, APPLICATION FOR EQUIPMENT FREQUENCY ALLOCATION before they can be used. If submitted, the DD 1494 will be rejected because the MURS frequencies are not allocated for federal usage.

Even though the MURS frequencies are not allocated for federal usage, regardless they can be and are still used by government and military agencies.

The five MURS frequencies are “licensed-by-rule,” which means they do not require the user to obtain a license. Therefore even government agencies do not need a frequency clearance for MURS devices.

For military applications, there may still be a need to evaluate MURS radios for Hazards of Electromagnetic Radiation to Ordnance (HERO) Impacts for each facility due to the types of ordinances stored there.

Got to to see the MURS equipment available.

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Wireless Security Gate Intercom

Wireless System Eliminates Expensive Trenching And Greatly Reduces Installation Cost

A wireless security gate intercom provides long range, 2-way voice communication to a two-way radio or wireless intercom. They can be used to open gates or doors from remote locations, which means monitoring personnel do not have to be confined to a desk.  These intercoms are also called “wireless call boxes” and are essentially long-range two-way radios in a water and vandal resistant case with some added features. There are no air-time or telephone service fees with these systems.

Wireless Intercom

Wireless Intercom

A wireless gate intercom makes it possible to quickly implement a communication system without expensive and messy trenching. These gate opening intercoms have a range of up to a mile, or even further with use of external antennas.

These call boxes use either UHF or VHF frequencies to communicate over long range. Most of these wireless frequencies require an FCC license, but the VHF version has several unlicensed frequencies. These call boxes can be programmed to be compatible with virtually any brand of VHF or UHF business band radio.

If the gate application requires unlocking a gate or door from a remote location, then a call box with a relay that can be controlled by pressing a button on a wireless intercom or two-way radio with the 2-tone encode feature is needed. A callbox with an entry keypad is also available that enables people to enter a code at the call box to open the gate or door.

When visitors press the button on the callbox it sounds a call tone on a handheld two-way radio or wireless base station intercom. Monitoring personnel can speak to the visitor and then press a bWireless Security Gate Intercom Application Bulletinutton that activates a switch output that can be used to open or close a gate, turn on a light, sound an alarm, or any application where remote control of an On/Off switch is required.

Some call boxes also have a sensor input that allows them to operate as a motion detection, tamper, or vehicle detection device. These callboxes send a warning tone when a change in the switch/sensor status is detected. One call box even has the ability to send a pre-recorded voice message when the switch status changes.

The callbox with voice messages can also play a message 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 call boxes location or it could be an emergency message of some type.

If no AC power is available at the gate, these callboxes can be powered by six D-cell batteries or by a solar power system.  If AC is available, an optional AC to DC 12 volt transformer is available.

If several callboxes are in use and the location of the unit calling needs to be known, a unique numeric identifier can be transmitted to a radio that has the ability to decode this identifier. This is like having a telephone with Caller ID capability. Or if fewer than five callboxes are needed, then separate channels can be assigned for each callbox.

For wireless gate communications, a wireless intercom like the Callbox XT Outdoor Wireless Intercom offers clear wireless voice communication and remote gate unlocking, quickly, without expensive trenching and monthly air-time fees.

These products are available at

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