CCTV or Audio Video switchers are popular in India for monitoring mutiple locations using CCTV Cameras. As there are multiple cameras and user can watch only one channel at a time, job of the switcher is to select the desired video and audio signal out of installed CCTV and show it on the video monitor.

User can select any channel using IR remote control.

This product can also be put in auto mode where after every few seconds next channel is selected. This way user can just keep watching various channels, each for few seconds.

The time for each channel can be set using IR handset. The channels that need to be skipped will have time of zero.

The volume level for audio for selected channel can be increased or decreased (or even muted).

Models with two way audio will send the voice of user to selected CCTV Camera. An inbuilt speaker in camera will amplify the voice and the persons present there can hear the instructions or what ever is being send by the user at monitoring station.

The basic building blocks are as follows

1. Display (four digit numeric display) - This shows the selected channel, (remaining) time for each channel. It also shows the volume for selected channel when setting volume level. Display are seven segment multiplexed and are controlled by Micro Controller digital pins.

2. IR sensor - This received the IR transmission sent by IR Hamdset, converts it to TTL signal and sent to Micro Controller.

3. EEPROM - This saves various parameters like, last channel being viewed, time for each channel, volume for each channel etc..

4. Signal Output Buffer - Selected channel number is output on seven digital lines of micro controller. These signals are buffered and sent to actual switcher circuit.

5. Audio/Video Switching - This is actual selection of analog signals from various CCTV camera. We use CMOS 4051, which is a popular analog ic with 8 to 1 selector switch. Multiple 4051 are used as per the design.

6. RS485 interface - This is optional interface circuit, where selected channel number is sent on RS485 port to a remote location switcher. Advantage of this is that actual switching (Audio/Video Switching Block) takes place at remote end and it saves lot of wiring issues. This however needs one extra box and a micro controller at remote end.

7. Audio Controller - This adjusts the volume of selected audio signal.

8. Mike and Audio Amplified (optional) - This is used only in two way audio systems. Here a mike picks up the voice of user at monitoring station and amplify and send it to the selected CCTV Camera. Another amplifer in the camera will amplify the audio signal and persons present in and around the selected CCTV will hear the voice/instructions. In normal case the mike at monitoring station is disconnected. It is only when user need to speak to the persons around selected CCTV Camera by pressing TALK switch on remote handset, then the mike gets activated.