Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [modem]

A modem (modulator-demodulator) is a device used to transmit and receive digital data over an analog communications channel. Common examples are PC modems that use an analog telephone line and wireless modems that use RF (radio frequency).

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Difference between Hirose U.FL and IPEX connectors

Both these connectors are used to connect antenna to Mini PCI cards. Wikipedia does not explain the difference between those naming issues: U.FL, IPEX, IPAX, IPX,[1] AMC, MHF and UMCC is a miniature RF connector for high-frequency signals up to 6…
Olivier
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Typical GSM current profile

I'm working with GSM modem and I'm wondering if anyone has come across any sort of measured or typical GSM current profiles for various actions such as: Connecting to base station Sending a SMS Voice call During an active data connection I know…
Joel B
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Best method for sending data over a mono audio channel

I'm looking for a way to send binary data over an audio channel on a video/audio transmitter. This will be an add-on feature to my product because it already has an audio interface. I'm hoping to be able to reach about 1 kbit/s data rate at a…
Thomas O
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Can modems be used to communicate with RC Submarines?

With reference to this video"R/C Sub, Scratch-built From Sewer Pipe" when the sub went to deep it lost the signal to the RC receiver. Question: Since water transfers sound better than radio waves would it be possible to connect two 33.3kb/s modems…
user3045
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Do DSL / ADSL modems have an ADC with ~ 2 MHz sampling rate?

For fun and no real practical use, I'm trying to design a DIY modem that can transmit data over an audio line, like old 56k modems did. I'm studying how to pack bits of data efficiently in a 1k-15k audio spectrum, such that I'll be able to…
Basj
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Audio filtering circuit with capacitor shorted

I was looking at the Adafruit FONA cellular network modem breakout board schematic and found something that I can't quite understand. The breakout board has an audio input and output that both goes into the SIM5320A modem through a filter. I found…
Pier-Yves Lessard
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FCC certification for nrf24l01+

Is nrf24l01+ from Nordic Semiconductors FCC certified ? It is hard to find out from their datasheet whether FCC approved ? Is it FCC approved ? If it is approved and I use it in my PCB and control it via my ARM cortex processor, do I need to get the…
bhuvan
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LDO vs switching regulator

We've currently got a PCB that needs to power a modem and a microcontroller. The PCB is powered via a battery (12V - 30V range). The modem and the microcontroller have separate power lines. The microcontroller + peripherals consumes about 200mA,…
ddewaele
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Sizing the DC/DC inductor for only momentary high currents

My DC/DC setup is going to power a GSM modem. The behavior of these modems is that they typically consume only a few tens of milliamps, but when transmitting they are drawing 2A for microseconds. On average these pulses can add up for an average of…
Szundi
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Two devices sharing the same coaxial cable, what frequency channel should I chose?

The 2-stories house is equipped with a coaxial cable that has wall plugs in 1st and 2nd floors (it's also connected to the antenna on the roof). Our IAP installed a modem for Internet (Arris CM820C) which frequency ranges are, according to the…
Déjà vu
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Establish connection between analog and GSM modem

I want to know if I can call a GSM modem (a SIEMENS MC55) from a normal analog (PSTN) modem. If so, how do I have to configure the GSM and the analog device? I've read about the +FCLASS and +CSNS commands but the connection doesn't work - I'm…
sebastian
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Why download and upload speed is different in 56k modems?

I have read that this is due to the absence of an A/D or D/A conversion (only) in the down stream which would normally introduce some quantization error. This conversion is present in the upload, so the speed is then 33k. I can understand that some…
nikos chatziathanasiou
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(When) Can I use Cat5e wiring to carry a POTS signal to a DSL modem?

According to this answer by @asndre, It is very bad idea to use Cat5e-based wiring/cabling to establish a xDSL connection. However, my telephone/internet provider technician recommended -- and gave me 100ft of -- Cat5e cable to carry the…
LarsH
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Performance Analysis of PLC Modem

I'm an electronics and communications engineering student undertaking a project regarding the occurrence of Electromagnetic Interference (EMI) in power line communications (PLC). I would like to ask if anyone has any suggestions on how to do a…
Eager Engineer
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56k Single Chip Modems

I'm currently working on a project that's intended for getting old electronics that access networks through the use of a phone line to access the internet. To do this, I'm emulating a simple phone system, but I will need a modem (single chip modem…
Tristan
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