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output impedance

impedance that a device presents to its load

3.1.37

peak-to-peak

amplitude (voltage) difference (as displayed on an oscilloscope) between the most positive and the most negative peaks of an electrical signal

3.1.38

phase alternate line

phase of the colour carrier is alternated from line to line, taking four full pictures for the colour to horizontal phase relationship to return to the reference point

3.1.39

physical transmission path

combination of the transmission medium and necessary amplifiers and other equipment to form a transmission path with one or more transmission channels

3.1.40

pixel depth

number of bits used for a pixel, determining the maximum number of colours that can be displayed at one time

3.1.41

resistance

real (non-reactive) part of the impedance of a circuit

3.1.42

return loss

difference between the power incident upon a discontinuity in a transmission system and the power reflected from the discontinuity

3.1.43

root mean square

measure of the effective level of a video signal or alternating current

3.1.44

saturation

intensity of colour

3.1.45

signal level

r.m.s. voltage measured during the r-f signal peak, expressed either in microvolts referred to an impedance of 75 Q, or in dBmV, the value in decibels with respect to a reference level of 0 dBmV, which is 1 mV across 75 Q

3.1.46

signal to noise ratio

signal expressed in decibels that relates how much stronger a signal is than the background noise

3.1.47

staircase

test signal commonly used to check luminance gain linearity

3.1.48

subcarrier

signal that is modulated by colour information to form a chrominance signal

3.1.49

S-video

composite video signal separated into the luminance (Y) and the chrominance (C)

3.1.50

sync

means of synchronizing signals with timing pulses to insure that each step in a process occurs at exactly the right time

EXAMPLE Horizontal Sync determines exactly when to begin each horizontal line; vertical Sync determines when to start at the top-left of the screen for a new field.

3.1.51

television lines

maximum number of changes between light and dark on a picture across 3/4 of the width results in the resolution of a CCTV system, measured in TVL

3.1.52

termination

load at the end of a cable or signal line used to match the impedance of the equipment being used to prohibit signal reflections back toward the source

3.1.53

terminate

provide termination for a signal line, or several signal lines, at the end of a cable

3.1.54

test pattern

chart or special video signal sample for checking overall performance of a CCTV system containing various combinations of lines and geometric shapes by viewing a monitor for fidelity of the output pattern

3.1.55

test signal generator

instrument providing a variety of known test and synchronization signals for the characterization of CCTV systems

3.1.56

transmission

electrical transfer of a signal, message, or other form from one location to another for example the transfer of a video waveform from point to point by conductive cable or fibre

3.1.57

transmission channel

combination of the transmission medium and necessary amplifiers and other equipment to form a connection between video equipment in a CCTV system

3.1.58 transmission media physical means used for the transmission of video signals, such as cable transmission

3.1.59 transmission methods means used for the transmission of video signals, such as wireless or wired transmission

3.1.60 transmission system combination of equipment and media that provide the transmission of video signals between the various CCTV equipment

3.1.61 vectorscope specialized oscilloscope which demodulates the video signal and allows visual checking of the phase and amplitude of the colour components of a video signal

3.1.62 video graphics array analogue signal with TTL level separate horizontal and vertical sync at a 15-pin connector with a horizontal scan frequency of 31,5 kHz and vertical frequency of 70 Hz (Mode 1, 2) and 60 Hz (Mode 3) 3.1.63 video signal electrical signal that includes all the information present in the television picture together with the necessary synchronizing signals 3.1.64 video switcher device that accepts inputs form a variety of video sources and allows the operator to select a particular source to be sent to the switcher output(s) 3.1.65 waveform monitor oscilloscope designed especially for viewing the waveform of a video signal

For the purposes of this document, the following abbreviations apply. APL Average Picture Level

В Blue

C Chrominance

Cb blue-difference chroma components

CCIR Comite Consultatif International des Radiocommunications

(International Radio Consultative Committee) CCTV Closed Circuit Television

Cr red-difference chroma components

CVS Composite Video Signal

dB Decibel

DC Direct Current

DDC Display Data Channel

DDWG Digital Display Working Group

DMT Display Monitor Timing

4 Analogue video signal transmission requirements

4.1 General

The properties of the transmission system shall be provided in a specification sheet covering the items in this clause.

The specifications stated by the manufacturer shall be those determined under the standard operating conditions, indicating the type and requirements for the transmission media and such additional information that enable the system designer to achieve the requirements of this European Standard.

The common requirements of a video transmission system are given in 4.2 to 4.7. The additional requirements for the transmission of PAL colour video signals are given in 4.8 to 4.11.

The minimum requirements and specification items are given in 4.2 to 4.15.

The source and load impedance of a transmission system shall be 75 Q on the unbalanced coaxial input and output. The impedance tolerance is specified in 4.2.2.

The return loss in the inputs and outputs shall be better than 20 dB from 0,1 MHz to 5 MHz.

The nominal input and output signal levels shall be 1 K_pp. in accordance with CCIR Report 624-4 for 625 lines, 50 fields per second and, in case of colour, PAL colour coding. The transmission equipment shall be capable of operating within specification for a video component in the composite input and output signals of up to 1,0 K_pp. The signal level of the synchronization components in the composite video signal shall be 0,3 K_pp ± 0,05 И_рр. For colour signals, the amplitude of the burst component in the composite video signal shall be 0,3 K_pp ± 0,05 И_рр.

The equipment shall be capable of operating at an input signal with a horizontal frequency (f_h) of 15 625 Hz ±1 % and a vertical frequency of ²/₆₂sX /_h and a subcarrier frequency of 4,43 MHz ± 50 ppm.

The equipment shall be capable of operating correctly when presented with a video input signal having a DC component of 0 V ± 2 V.

The DC voltage in the terminated output signal shall not exceed 0 V ± 2 V.

The insertion gain of the transmission system shall be 0 dB ± 1 dB on the nominal 1 input signal.

The bandwidth and frequency response requirements of the video transmission system are determined by the linear distortion requirements given in 4.4.2 to 4.4.5.

The waveform distortion on a line time square wave signal shall be < 5 %.

The waveform distortion on a 50 Hz square wave shall be < 5 %.

The peak overshoot of the video signal measured at blanking level shall not exceed 0,25 V.

The peak overshoot shall settle to < 0,02 V within 5 s.

During the test, the video and synchronization signals shall not be clipped or compressed by more than 20 % of their original value.

The 2T pulse to bar ratio shall be < 5 %.

The 2T К-factor (K_(2T)) shall be < 5 %.

The signal to noise ratio of the transmission channel, which includes the accumulated noise in cascaded amplifiers and cable loss correction, shall be > 46 dB.

Interference from e.g. data channels, other video channels, audio channels, shall not cause visible disturbance to the picture.

The luminance non linearity shall be < 10 %.

The gain error shall be < 20 %.

The delay error shall be < 100 ns.

The differential gain error shall be < 10 %.

The differential phase error shall be < 10 °С.

The apparatus shall withstand the environmental influences of the specified service environment.

The service environment is defined by selection of one of the following four classes according to EN 50130-5:

• Class I: indoor but restricted to residential and office environments;

• Class II: indoor in general;

• Class III: outdoor but sheltered from direct rain and direct sunshine, or indoor with extreme environmental conditions;

• Class IV: outdoor in general.

As a minimum, the equipment shall withstand exposure to the environmental influences of the tests given in Clause 7 for the specified service environment.

The electromagnetic radiation of the transmission equipment shall conform to the relevant standards of the application, as a minimum it shall conform to EN 61000-6-3.

The sensitivity to electromagnetic interference of the video transmission equipment shall conform to EN 50130-4.

The electrical safety of the video transmission equipment shall conform to the relevant standards of the application, as a minimum it shall conform to EN 60065 or EN 60950-1.

5. Analogue video signal transmission test conditions

   1. Introduction

The test requirements described in this clause have been devised to measure the performance of CCTV transmission systems in a manner corresponding to their normal operation. The tests cover the most important transmission properties and enable comparisons between measurements taken at different laboratories.

To guarantee sufficient accuracy and reproducibility in the measurements, the test shall be conducted in certain specified conditions.

Test equipment shall be calibrated to tolerances in relation with the required accuracy of the respective measurements.

The test equipment normally required is:

1. a video wave form monitor or oscilloscope. Preferably with facilities for triggering of the sweep from field or line pulses of the CVS signal;

2. a monochrome or colour video monitor;

3. a video noise meter, capable of CCIR weighted noise measurements in accordance with CCIR Recommendation CMTT 567-3;

4. a video signal generator providing appropriate test signals;

5. a video vectorscope.

NOTE Video analysis equipment combining some of the above mentioned functions may be used.

List of signals (also refer to CCIR Recommendation CMTT 567-3:1990, Annex 1, Part C).

• Signal A: half frame white and black bar signal (see Figure A. 1);

Signal B: pulse and bar signal (see Figure A.2);

• Signal C: frequency burst (see Figure A.3);

• Signal D1 and D2: grey scale signal (see Figure A.4 and Figure A.5);

• Signal F: 20T pulse (see Figure A.6).

The transmission equipment shall be connected and adjusted in accordance with the manufacturer’s recommendations, for the recommended cables and up to their maximum specified length. Unless otherwise specified in the tests, the system shall operate at nominal input and output levels and terminated in a standard load impedance of 75 Q ± 5 %.

Unless otherwise specified, the atmospheric conditions in the laboratory shall be the standard atmospheric conditions for measurements and tests, specified in EN 60068-1:1994, 5.3.1, as follows:

temperature: 15 °С - 35 °С;

relative humidity: 25 % - 75 %;

air pressure: 86 kPa - 106 kPa.

5. Analogue video signal transmission performance tests

   1. Input and output signal levels

      1. Principle

To verify the minimum and maximum signal amplitude at the transmission equipment input and output terminals.

A TV-signal generator providing grey scale signal D2 (Figure A.5) shall be connected to the terminated equipment input. The amplitude and the blanking reference voltage of the input and output signals shall be monitored on a DC-coupled waveform monitor.

The composite video test signal applied at the input shall be 1,35 K_pp (luminance part), of which the amplitude of the synchronization signal shall be 0,3 K_pp ± 0,05 K_pp. Superimpose a positive and negative DC-voltage on the video test signal such that the blanking level of the test signal reaches + 2 V and - 2 V. Allow some time for the equipment to stabilise to the new input condition.

The transmission equipment shall be capable of operating over the full test without noticeable distortion of video signal at the output. Clipping or crushing of the video and synchronization signals at the equipment output are not allowed.

To verify ratio of the output signal to the input signal of the transmission system.

A TV-signal generator providing signal element B3 (Figure A.2) shall be connected to the equipment input. The amplitude and the blanking reference voltage of the input and output signals shall be monitored on a DC-coupled waveform monitor. The input source impedance and output termination impedance shall be 75 Q ± 0,5 %.

Measure the peak-to-peak voltage of test signal part B3 (Figure A.2) at the input and at the output of the transmission system. The amplitude and timing of the test signal is measured between the centre point of the bar signal and the blanking level.

The transfer gain of the transmission equipment shall be 0 dB ± 1 dB after initial adjustment.

To define the termination impedance at the input and source impedance at the output terminals of the transmission equipment by the reflection damping.

A TV-signal generator providing a grey scale signal shall be connected to the terminated equipment input. The amplitude and the blanking reference voltage of the input and output signals shall be monitored on a DC-coupled waveform monitor.

The input and output impedance and return loss shall be determined by measuring the return factor, using dedicated reflectometer devices or by using a Wheatstone bridge in accordance with Figure 1. The signal generator shall be able to provide a frequency sweep from 0,1 MHz to 5 MHz. The differential capacitor is adjusted to achieve proper high frequency balancing of the source. A_n is the reference resistor (75 Q) with a tolerance of less than 0,5 %, A_x is input or output impedance of the transmission equipment for measurement of the input and output impedance, respectively. The oscilloscope is used to measure the unbalance voltage U₂ as a function of the applied input voltage U_}.

Figure 1

The relation between return factor and input and output impedance is given in Formula (1):