OSCILLA SM960-C - Page 8

ID: 1745 / ver. 201
8
4. LEVEL OFFSETS adjustment (mode 4)
RETSPL table for TDH39 telephone (ISO-389-1995)
Hz
dB
125
250
500
750
1000
1500
2000
3000
4000
6000
8000
45
25.5
11.5
7.5
7
6.5
9
10
9.5
15.5
13
RETSPL table for DD45 telephone
Hz
dB
125
250
500
750
1000
1500
2000
3000
4000
6000
8000
45.5
28
14
7.5
7
9
9.5
11
12.5
18.5
17
Narrow band masking
The masking level should be 3 dB higher than the tone’s, at all frequencies. Adjust the masking level
without bandpass filter. As the masking level is changed automatically when the tone is adjusted, it is
normally not necessary to adjust, but due to the telephones’ frequency response at high frequencies,
adjustment should be done at least at 4000, 6000 and 8000 Hz. Choose between tone and noise with
the channel 2 input selector.