Security and fire control system

DETAILED DESCRIPTION FIG.
1 is a functional block diagram of a video transceiver.
The video transceiver is used to transmit and receive audio and video signals over a Public Switching Telephone Network (PSTN).
Those skilled in the art will appreciate that the video transceiver can easily be adapted to work on ISDN and ADSL telephone lines as well.
The video transceiver includes a keypad circuit 25 which provides a user interface to a transceiver circuit 21.
The transceiver circuit includes an audio/video circuit 23 coupled to a controller circuit 27.
The controller circuit 27 is responsible for managing all operations of the video transceiver and coordinating the flow of data into and out of the system.
The controller circuit 27 preferably includes memory (not shown) for storing a number of telephone numbers that are automatically dialed by the audio/video circuit 23 upon the occurrence of a certain event.
Alternatively, the controller circuit 27 commands the audio/video circuit 23 to dial the telephone number inputted by the user on the keypad circuit 25.
The audio/video circuit 23 accepts commands from the controller 27 and provides an interface to the PSTN telephone line.
During transmission, the audio/video circuit will accept video and audio inputs from external sources and commands from the controller circuit 27 and format the information for delivery over the PSTN telephone line through the modem in/out line 14.
The video input 16 is typically a video camera signal having a standard video output such as NTSC or PAL.
NTSC and PAL are video standards well known in the art that specify line and field rates and include color information encoding.
These standards provide composite video signal for luminance and color information together in one signal.
An NTSC compatible system operates with 525 lines per frame and 30 frames per second.
A PAL compatible system operates with 625 lines per frame and 25 frames per second.
The audio input 18 typically comprises voice or speech signals that vary in amplitude and frequency