Study Exercises (Cont)

Telephone Circuit Conditioning
Page Navigation
46

When the line under test is patched to the TTS-58A, the instrument

receives all noise on the circuit, including white noise.

However,

white noise has no affect on the TTS-58A because this instrument uses

threshold circuit.

spring-driven timer.

filter to block the white noise.

weighting circuit to discriminate against white noise.

Assume that you are calculating the S+N/N. If the TTS-37B indicates a

level reading of -4 dBm with signal applied, and +46 dBrn when the

signal is removed, the S+N/N is

38 dB.

44 dB.

40 dB.

46 dB.

SITUATION

Assume that you are conditioning a circuit to parameter S3.

This

parameter specifies that harmonic distortion must be less than -40 dBm0 when

a test frequency of 700 Hz is introduced at a level of -10 dBm0. Level at

TLP is -12 dBm.

Exercises 7 through 10 are based on this situation.

A test frequency of 700 Hz is used in the harmonic distortion test of

telephone carrier-channel rather than 1,000 Hz because the

fourth harmonic of 700 Hz lies within the voice passband of the

channel.

test tone of 700 Hz will not interfere with other tests performed

at 1,000 Hz.

700 Hz test tone frequency is closer to the center of the voice

passband than 1,000 Hz.

interfering affect on a listener of the 700 Hz tone is less

severe than the 2,000 Hz tone.