EN 62820-1-2-2017 pdf download.Building intercom system – Part 1-2: System requirements – Building intercom systems using the Internet protocol (IP) (IEC 62820-1-2:201 7).
6.3.3 Test of echo return loss
6.3.3.1 Objective test of echo return loss
a) The test environmental noise shall not exceed 30 dB(A). It is recommended to conduct the test in a full-anechoic chamber or semi-anechoic chamber. If EUT has volume control, it shalt be set to the maximum level before the Larsen effect appears. The CSS test signal illustrated in Figure 2 shall be used. During the test, the communication of EUT shall not be interrupted.
b) The total time of two-way point-to-point audio delays. 7’, shall be tested separately and recorded according to 63.2. If the total time of the two-way transmission of the EUT is less than 100 ms. there is no need to do this test.
C) The audio signal generator shall generate the CSS test signal through the artificial mouth to initiate audio in the local terminal. Test signal is transmitted from the local unit to the remote unit. When the test signal returns back it is measured by the microphone at the local unit after a delay 7’.
d) Use an acoustic measurement analyser in 1/3 octave frequency interval to measure and record the ear bearing pressure P1 of the last 100 ms from the fourth CSS signal group within 200 Hz to 4 000 Hz. The echo return loss at the remote unit shall be calculated by differentials between sound pressure of the MRP at the sending unit and the voice signal average sound pressure from the remote unit, using the following formula
where
I is the serial number of frequency. The corresponding central frequency shall comply with IEC 62820-1-1:2016. Table A.1;
P1 is the average sound pressure on the frequency bandwidth.
e) Based on the test method mentioned In C) to d), repeat the test measurement for 10 times continuously and take the average as the test result that shall meet the requirements of
5.2.2.
NOTE The suggested interval between two measurements is over 1,5 S.
6.3.3.2 Subjective evaluation of echo return loss
Subjective evaluation of echo return loss shall be conformed according to Annex B.
6.3.4 Test of audio switching time
a) This test shall use two groups of test signals A and B. Test signal A shall use 10 continuous CSS signals, where the duration shall be longer than the expected time that the single direction transmission of BlS can become stable (see Figure 3). Test signal 8 shall consists of four CSS signals, the first pulse of the CSS signal is used for measurement (see Figure 4).
b) Figure 5 shows the audio switching time progress. Separately measure the audio time delay from one terminal to the other in both directions based on the test method specified in 6.3.2.
c) The audio signal generator shall generate test signal A through the artificial mouth to initiate the audio transmission in the local terminal and record the initial time. When the remote terminal finishes playing the 10th CSS pulse the MRP of the remote terminal shall generate the test signal B.
d) Use microphone in the local terminal to record the output signal coming from the remote terminal and measure the time, TDS, from the start of the first CSS signal B until it reaches 3 dB below the average normal audio transmission amplitude. The audio switching time Ts calculated by the difference between T0 and TD2. The test result shall meet the requirements of 5.2.3.
6.4.3 Image resolution test
Test methods specified in IEC 62820-1-1:2016, Clause B.3 shall be followed. The test results
shall comply with the requirements set forth in 5.3.2.
6.4.4 Frame rate test
a) The test signal shall be generated by continuously activating the 10 horizontal LEDs at the centre of the LIG device.
b) Adjust the frequency of the LIG (f) from 1 Hz (each led is activated once every second with a flash time of 11 (101) s) upward so the 10 LEDs will light up one by one horizontally according to the frequency set. Watch the image on the VRD and stop increasing the frequency of the LIG when the LEDs appear to stop moving on the VRD, This state shall be maintained over 10 s without any drop to ensure its validity.
C) Record the value of frequency on the LIG. This value is the frame rate (jr). The test result shall conform to the requirements set forth in 5.3.3.
6.4.5 Video delay test
a) This test should be carried out alter 6.4.4, using the frame rate (fr) of EUT as the frequency [of LIG. Use the continuously changing image generated by the LIG on the 10 x 10 LED matrixes as the test signal.
b) The tested VCD shall capture the image generated by LIG A. At the receiver end, a digital video camera shall continuously capture image frames, with a frame rate Jr during 3 s, of the received video image on the VRD display together with the image generated by LIG B.
C) For each captured image frame within the 3 s. compare the location of active LED on the LIG B and on the VRD display In the same frame and count the number of the LEDs (n) difference between them. Video delay of this picture Is (1 000 x nt Ifr (ms).
d) Filter the values discarding the 10 % of higher values. The resulting highest value is the video delay. The test result shall conform to the requirements set forth in 5.3.4.
NOTE If the BIS is able to mute audio or reduce audio volume to avoid Larsen effect the test can be conducted with only one LED matrix, locating it in front of the VCD and beside the VRD It will represent LIG A or B indistinctly in the test description.
6.4.6 Lip sync test
The test condition and method should meet the requirements of both 6.3.2 and 6.4.5.
The audio signal generator plays ten groups of test signals, each one with four CSS pulses (Figure 6), and each group separated by a pause of 400 ms, with a total test signal length of 16 586,2 ms. The first three CSS signals in each group are used for training; the fourth will be used to measure the audio delay (as described in 6.3.2) and also to trigger, in the falling edge. the digital video camera to capture one image simultaneously. Therefore a measurement of audio delay and video delay are taken at the end of every group test signal, I.e. 10.EN 62820-1-2-2017 pdf download.