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18 Threads found on edaboard.com: Telephone Noise
You did not describe the "background noise". Is it high frequency hiss, low frequency hum, low frequency rumbling or acoustical feedback howling? The design of the 741 opamp is 47 years old. It cannot produce high audio frequencies and was never intended for audio (maybe for a telephone?) so it is noisy with hiss and rumbling. Your circuit also
An LM386 is a power amplifier designed to drive a speaker. Its output noise (hiss) is probably too high for it to be a mic preamp. Use a low noise audio opamp instead. A telephone has a narrow bandwidth because 138 years ago that was the best they could do. It cuts the natural low frequencies of an adult male voice (my voice is not deep but (...)
My telephone Line (Normal PSTN ) have high noise in the line . What are the possible reason for noise in the telephone line ?
I've witnessed it in commercial products too. A PLL inside a telephone product that went out of lock if you hit the keys too hard! It took some persuading to get the designer to even consider that might bet the problem but on analysis, that's exactly what was happening. Brian.
It differs between peak and average power. In CDMA telephone systems during times of no speech, the power is reduced and a simpler spreading is used. The background noise is probably suppressed by turning down the audio gain at the other receiver.
The two wires of a telephone line are balanced so that each wire has the signal out-of-phase to cancel hum pickup. Your circuit grounds one wire of the telephone line which causes the other wire to act like an antenna that picks up all kinds of interference. Usually an audio transformer is used to keep the telephone line balanced and it (...)
Dear all why when there is a mobile near an ordinary telephone we hear some noise in it (while a call is coming to the mobile) although the mobile works in >800Mhz and telephone <<20khz !!! thanks alll bye
Hi all, I need an amplifier that will enhance my telephone signal. The signal is sinking into noise due to extensive cabling. Has anyone met or designed something similar? Thanks, D.
I'm working in the project "telephone recording 4 channels". I'm using the LM386, but I have some troubles. When I test the board, I hear very much the noise. Can you help me. I want to replace LM386 with other ICs. Thank you very much
you can buy a better cordless telephone now. :)
Hi all, I have designed a cordless telephone,but the background noise is uncomfortable,i want to improve it.Anybody kindly share me your experiment and documents about how to suppress it? Thank you.
Hello, I'm going for a job interview and a big part will be questions on delta-sigma A/D converters. I am wanting to prepare and would appreciate some feedback as to what might be asked. BTW, it will be telephone interview at first. cheers, Ps I am familiar with the basic principle, i.e. noise shaping, quantization noise, (...)
i have a adsl broadband connection which my provider provides me using the standard telephone line., i am using a Router cum modem, i am facing a problem with my telephone line , whenever there is a little noise in the telephone line, my modem doesent shows the ADSL link and i am unable to connect. so i want to know is (...)
i have a adsl broadband connection which my provider provides me using the standard telephone line., i am using a Router cum modem, i am facing a problem with my telephone line , whenever there is a little noise in the telephone line, my modem doesent shows the ADSL link and i am unable to connect. so i want to know is (...)
FM transmission is analog. The quality is due to a better noise immunity of FM over AM. But you can modulate digital signals and send it over FM like you can send digital data over analog telephone line.
Rarely used? Like telephone and ethernet? Look inside any modern computer. Many high MHz and GHz twisted pair links. Differential noise immunity. Easy and cheap to manufacture.
dBm is power measured in milliwatts and expressed in dB above or below one mW. dBm0 is almost similar except it is power relative to a zero level that is different from 1 mW. dBmP is relative to Picowatts of noise psophometrically weighted (pWp) These terms come from copper wire telephone systems and go back 100+ years in some cases.
These curves are similar to the human ear's response to noise. Filtering telephone channel noise through them before measuring the noise output is a better predictor of perceived noise than measuring the