ALARM SYSTEMS, WIRE OR WIRELESS?
Hardwired systems use concealed or exposed wiring to connect the components. Even when wireless techniques are used for some of the system sounding devices are usually connected to the control with wiring. While the time and cost of installing the wire can be greater a hardwired system is not generally subject to “radio interference".
”Since all devices can be powered from a central power source in the control, individual batteries at each device are not required.
Wireless systems use radio frequencies to connect sensors to the control. In wireless systems hardwired or wireless methods may be used to connect the user controls to the control.
Battery Powered Transmitters
Small battery powered radio transmitters are used to signal alarms to a radio receiver in the control. When the battery wears out, it must be replaced or the transmitter’s signal can’t reach the control. Some use “household” batteries that last for about 10 months, while others use special batteries that last for several years.
If transmitters use the same signal supervision is sacrificed. Many systems supervise the signal strength and verify operation by monitoring each sensor at preset intervals. If the transmitter fails to check in a specified number of times over a preset period of time, an indication is made locally and or remotely that a sensor has failed to send a signal. This is distinctive from the alarm signal. Batteries can also be supervised by reporting when they fall to a predetermined voltage. This is also a distinctive signal. Transmitters may or may not use end of line devices on their protective circuits.
Each receiver and transmitter has a specific frequency or path (house code). Multiple transmitters can be connected to a single receiver. All transmitters may be setup to send the same signal or each transmitter can have its own identity
Premise Wireless Types
Supervised or non supervised
Single or multizone
Short or mid range
Integrated: combined with the control or Slave: separate from the control
Narrow band or spread spectrum
Some controls combine both wired and wireless features. Individual zones are factory or installer selected as wired or wireless.
Hardwired vs. Wireless
Hardwired and wireless systems each have an almost equal number of devoted fans. While there are applications that can only be done with hardwire and others that can only be done with wireless, most applications can be done either way. This leaves the choice to the installer and the alarm user. Hardwired systems are preferable in areas with high levels of radio frequency interference and in systems where maintenance of batteries in the transmitters would be a problem. Wireless systems are preferable in areas where concealing wires is difficult or when portability of the system is desired.
Uses existing electrical power and lighting wiring to send signals.
Can activate lights, receptacles, and audio/visual devices.
Some devices require an electrician to install.
May be activated by alarm or other control devices.
Devices will not communicate during power failures.
Normally not supervised. May require signal repeaters and signal bridge.
Be sure to check UL listing for proper application.
Line carrier systems use the existing electrical wiring at the alarm site to transmit the messages between the alarm system components.
Signals are sometimes multiplexed on the alarm sites power lines between the sensors and the control.
A more common use of line carrier technology is to send signals to lights or sounding devices in a home when the alarm is activated. Two problems with line carrier technology have limited its use. First, problems with the power lines, including outages, can prevent the signals from getting through. Many alarm sites have more than one phase or set of power lines, so that communication between the two phases may require special equipment.