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T ELEVISION - 2. EC 326 COMMUNICATION SYSTEMS UNIT - III. T Srinivasa Rao Dept. of ECE Bapatla Engineering College. Part 1. Vision characteristics and scanning systems, Composite video signal. Part 2 Camera tubes: Principle of operation, Image Orthicon, Vidicon , Plumbicon . Part 3
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TELEVISION - 2 Communication Systems (EC-326)
EC 326 COMMUNICATION SYSTEMSUNIT - III T Srinivasa Rao Dept. of ECE Bapatla Engineering College
Part 1 Vision characteristics and scanning systems, Composite video signal. Part 2 Camera tubes: Principle of operation, Image Orthicon, Vidicon, Plumbicon. Part 3 Block diagram of broad cast TV transmitter Block diagram of broadcast TV receiver. Communication Systems (EC-326)
Simplified cross-sectional view of a Vidicon TV camera tube Communication Systems (EC-326)
Elements of a picture tube Communication Systems (EC-326)
Signal transmission paths illustrating compatibility between colourand monochrome TV systems.R, G and B represent three camera tubes which develop video signals corresponding to the red, green and blue contents of the scene being televised Communication Systems (EC-326)
A Rectangular Picture Tube Communication Systems (EC-326)
Monochrome Picture Tube • One Electron Gun • Continuous phosphor coating Colour PictureTube • Three electron beams • Three phosphors. Communication Systems (EC-326)
Electron Gun • Control Grid • Accelerating Grid • Focusing Grid Communication Systems (EC-326)
Vidicon camera tube cross-section Communication Systems (EC-326)
Circuit for output signal from a Vidicon camera tube Communication Systems (EC-326)
Leaky Capacitor Concept Communication Systems (EC-326)
THE PLUMBICON Target Details Output Signal Current Characteristics Communication Systems (EC-326)
Switcher for selecting any camera output to one monitor. A sync generator driving several camera units Communication Systems (EC-326)
Block diagram of a drive and sync pulse generator Communication Systems (EC-326)
Block Diagram of a Television Transmitter Communication Systems (EC-326)
Rear view of a black and white receiver with the back removed Communication Systems (EC-326)
Block diagram of a monochrome television receiver Communication Systems (EC-326)
CHOICE OF INTERMEDIATE FREQUENCY IN TV (i) Image Rejection Ratio (ii) Pick-up Due to Local Oscillator Radiation from TV Receivers (iii) Ease of Separation of Modulating Signal from IF Carrier at the Demodulator (iv) Image Frequencies Should Not Lie in the FM Band (v) Interference or Direct Pick-Up from Bands Assigned for other Services (vi) Gain Communication Systems (EC-326)
V S B CORRECTION Communication Systems (EC-326)
VIDEO DETECTOIN Communication Systems (EC-326)
Detector and filter circuit of a radio receiver Communication Systems (EC-326)
REQUIREMENTS (a) The detector load must provide a suitable impedance as seen through the diode, at input of the detector to tune and damp secondary of the last IF coupling circuit correctly. (b) The detector load must remove from the output, the IF content in the signal as much as possible. For this purpose the load usually includes one or two low-pass filter sections. (c) The detector load should have a trap circuit (a series rejector circuit) for separating the intercarrier sound signal. (d) The detector load must also include a provision to boost the higher video frequencies to compensate for the loss due to input capacitance of the video amplifier. Communication Systems (EC-326)
FUNCTIONS OF THE COMPOSITE VIDEO SIGNAL Communication Systems (EC-326)
SOUND SIGNAL SEPARATION Communication Systems (EC-326)
Block diagram of AGC system Communication Systems (EC-326)
High Voltage (EHT) Supply Communication Systems (EC-326)
Deflection Circuits Communication Systems (EC-326)
Operating Controls of a T V Receiver • Channel Selector • Fine Tuning • Volume • Tone • Contrast • Brightness • Vertical Hold • Horizontal Hold. Communication Systems (EC-326)
Next…Colour Television… Communication Systems (EC-326)