Question 9.3: A 1004 Hz test tone is transmitted over a telephone circuit ......
A 1004 Hz test tone is transmitted over a telephone circuit at 0 dBm and received at -16 dBm. Determine
a. The 1004-Hz circuit gain.
b. The attenuation distortion requirements for a basic circuit.
c. The attenuation distortion requirements for a C2 conditioned circuit.
Step-by-Step
a. The circuit gain is determined mathematically as
0 dBm − (−16 dB) = −16 dB (which equates to a loss of 16 dB)
b. Circuit gain requirements for a basic circuit can be determined from Table 1:
Table 2
c. Circuit gain requirements for a C2 conditioned circuit can be determined from Table 1:
Table 3
Table 1 Basic and C-Type Conditioning Requirements
| Attenuation Distortion (Frequency Response Relative to 1004 Hz) |
Envelope Delay Distortion |
|||
| Channel Conditioning |
Frequency Range (Hz) |
Variation (dB) |
Frequency Range (Hz) | Variation (μs) |
| Basic | 300–499 | +3 to −12 | 800–2600 | 1750 |
| 500–2500 | +2 to −8 | |||
| 2501–3000 | +3 to −12 | |||
| C1 | 300–999 | +2 to −6 | 800-999 | 1750 |
| 1000–2400 | +1 to −3 | 1000-2400 | 1000 | |
| 2401–2700 | +3 to −6 | 2401-2600 | 1750 | |
| 2701–3000 | +3 to −12 | |||
| C2 | 300–499 | +2 to −6 | 500–600 | 3000 |
| 500–2800 | +1 to −3 | 601–999 | 1500 | |
| 2801–3000 | +2 to −6 | 1000-2600 | 500 | |
| 2601–2800 | 3000 | |||
| C3 (access line) | 300–499 | +0.8 to −3 | 500-599 | 650 |
| 500–2800 | +0.5 to −1.5 | 600–999 | 300 | |
| 2801–3000 | +0.8 to −3 | 1000–2600 | 110 | |
| 2601–2800 | 650 | |||
| C3 (trunk) | 300–499 | +0.8 to −2 | 500-599 | 500 |
| 500–2800 | +0.5 to −1 | 600–999 | 260 | |
| 2801–3000 | +0.8 to −2 | 1000–2600 | 80 | |
| 2601–3000 | 500 | |||
| C4 | 300–499 | +2 to −6 | 500-599 | 3000 |
| 500–3000 | +2 to −3 | 600-799 | 1500 | |
| 3001-3200 | +2 to −6 | 800-999 | 500 | |
| 1000-2600 | 300 | |||
| 2601-2800 | 500 | |||
| 2801-3000 | 1500 | |||
| C5 | 300–499 | +1 to −3 | 500-599 | 600 |
| 500–2800 | +0.5 to −1.5 | 600-699 | 300 | |
| 2801–3000 | +1 to −3 | 1000-2600 | 100 | |
| 2601-2800 | 600 | |||
Table 2 Circuit gain requirements for a basic circuit
| Frequency Band | Requirements | Minimum Level | Maximum Level |
| 500 Hz and 2500 Hz | +2 dB and −8 dB | −24 dBm | −14 dBm |
| 300 Hz and 499 Hz | +3 dB and −12 dB | −28 dBm | −13 dBm |
| 2501 Hz and 3000 Hz | +3 dB and −12 dB | −28 dBm | −13 dBm |
Table 3 Circuit gain requirements for a C2 conditioned circuit
| Frequency Band | Requirements | Minimum Level | Maximum Level |
| 500 Hz and 2500 Hz | +1 dB and −3 dB | −19 dBm | −15 dBm |
| 300 Hz and 499 Hz | +2 dB and −6 dB | −22 dBm | −14 dBm |
| 2801 Hz and 3000 Hz | +2 dB and −6 dB | −22 dBm | −14 dBm |
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