Model Railroad Signal Circuits

Posted on Saturday, March 22nd, 2008 at 10:07 pm

model railroad signal circuits

Wireless security cameras are used in closed-circuit television systems (CCTV) for surveillance and monitoring. They transmit a video and audio signal to a remote receiver using radio frequencies. Most of these cameras do require wired power, although some models may use batteries or even solar power.

Analog wireless security cameras

Analog wireless cameras transmit their signal in the lower, radio frequencies of 900MHz, 2.4GHz and 5.8 GHz. Note that most of them operate over the 2.4 GHz band, the same band that a lot of household wireless appliances, such as cordless phones and video game controllers, operate on. Interference may result when using in the home.

The advantages of analog wireless security systems is they are lower cost than their digital brethren, and you can use multiple receivers.

The disadvantages are they may cause interference with other devices in the home. The transmission is not secure. the video signal quality is lower than digital, and any interference makes it worse.

900 MHz systems can be used in installations where the signal must go through drywall or even trees to reach the receiver. There is also not a lot of interference with other devices. Unfortunately there are only two channels available at 900 MHz.

2.4 GHz systems are more common, and there are 12 channels available, however, it is rare that you can find a channel that is not already in use by another wireless device.

5.8 GHz setups have a better chance of success, since there is less interference and there are 8 channels available (so you can have up to 8 cameras). The biggest challenge is the signal cannot go through many walls without lots of degradation.

Transmission Power

Lower cost 5.8 GHz systems most likely have a 10 milliwatt transmitter, which ideally can transmit to 300 feet with line of sight between the transmitter antenna and the receiver antenna. This rarely happens. This is a broad generalization and conditions such as distance, weather and clear line of sight affect this greatly.

When selecting an analog wireless security camera system, make sure you find out the transmission power and determine whether this will be enough to overcome any obstacles in your system.

Digital Wireless Security Cameras

Digital security cameras transmit digital information over high bandwidth radio frequencies.

The major disadvantage is the cost of the system. This maybe offset by the many advantages.

  • Advantages of a digital system are as follows:
  • Long range transmission of signal with no degradation – can go 450 feet with line of sight between camera and receiver
  • Very high quality audio and video signals
  • Can have two-way communication between camera and operator
  • High security of the signal.

Wireless IP Security Cameras

Wireless IP cameras are now available that can connect through a local area network over IEEE 802.11b/g WiFi systems. These include 2-way audio feeds, encryption, pan, tilt control and automatic night vision. These types of cameras have replaced the older digital wireless cameras, due to prevalence of Wi-Fi networks.

These are some things to consider when laying out your system.

Scott Watkins writes on a variety of technology topics, including ccd security cameras and CCTV IP Cameras. You can find out more at his websites.

Scott Watkins is an electrical engineer with over 18 years in the electronic imaging industry. He is now retired and follows his passion by writing on topics such as security cameras and systems, model railroading, healthy eating and sensible exercise.

Model Railroad Signaling System Part 6 (鉄道模型の自動閉塞信号)

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