A telephone, is a telecommunications device that converts sound into electronic signals suitable for transmission via cables

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2answers
57 views

Convert a ringing telephone voltage of 90V AC to 3.3V 1000mAh DC current so that it only triggers when the telephone is ringing?

How can I convert and step down a ringing telephone voltage of 90VAC current to 3.3V 1000mAh DC current so that it only triggers when the telephone is ringing? Bridge rectifier? Inductor? Step Down ...
0
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0answers
30 views

Building own (FAX) modem

I was thinking of constructing my own simple modem based on a micro controller, such as an Atmel ATMega16. I can get a USB stack for the micro, so that part is one thing, but I'm having trouble ...
-2
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1answer
78 views

Is full duplex speakerphone available as an embedded feature? [closed]

Full duplex speakerphones are clearly a complex signal processing problem, since you have to filter the device's speaker output from the microphone pickup. But is this a feature that is presently ...
0
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2answers
105 views

How to make an easy oscillator?

I want to make a very simple oscillator that produces the sound of telephone ringing (I want to make a ringer). I will not connect it to a telephone so the quality of the sound is not important. I ...
0
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0answers
24 views

Multiple phone (pstn or gsm) numbers in a single modem

Is there any way to receive calls to multiple numbers in a single modem in case of PSTN (land phones) or sim in case of GSM? I already know that for GSM, there are multi-sim modems available but I am ...
0
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3answers
59 views

RJ11 socket in Eagle libraries?

I am trying to add RJ11 (telephone wire) sockets to my PCB on Eagle but am having trouble finding it in the libraries. Is this a standard socket that is included or do I need to install some external ...
0
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0answers
27 views

How to adapt 3.5mm to 4P2C?

I am trying to make a cable so I can plug my old phone into my new smartphone. It has a 4P2C connector, and I have tried splicing the 4P2C cable and a 3.5mm cable together but it didn't work. How ...
15
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6answers
2k views

Unplugging a router from the wall socket

When the internet appears to have crashed, the service provider invariably gives this advice as a first line remedy: unplug the router from the wall socket, then wait 5 minutes, then plug it back in. ...
0
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1answer
50 views

G.711 for dummies

I am in midst of some online telephony course, and there are questions regarding which I have no one to ask but this community. G.711 volume encoding. I have some difficulty to understand how ...
1
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2answers
187 views

How ADSL Demodulates (restores the order) the signal for dummies

I am not an electric engineer so sorry for questions that might miss some fundamentals. I am trying to understand the ADSL modem. The ADSL modem sends the data over different frequencies in ...
0
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4answers
95 views

What is this electronics component?

What is the yellow component shown here? This is off a Outlet USB phone charger.
0
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1answer
71 views

bluetooth headset with LCD and memory

I was wondering if it is possible to create a bluetooth device which would have a LCD screen and some memory (1kb) for making and receiving calls. From my research ( and I am far from an EE, but ...
2
votes
1answer
65 views

Wireless telecom system (cellular with Erlang and spectral efficiency)

We have a spectrum of 20MHz that we will use on a wireless cellular system, which requires 50kHz per channel. The system is using cluster size K = 4 and the radius of every cell is R = 1 km. a) ...
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1answer
53 views

Cell in Cellular communication

When they talk about the "cell" in cellular communication, they often refer to the shape of hexagon. If I am correct, this is probably the coverage area of the transmission base tower. SHouldn't be ...
2
votes
2answers
246 views

Is it ok to use an old phone as an universal battery charger?

We know that a charger is just an adapter that supplies a constant voltage (5 volts usually). The actual charging circuit is in the phone itself. With a bit of soldering and wiring, can I use my old ...
0
votes
1answer
91 views

The simplest circuit to translate from RJ11 to my PC [closed]

Assuming that you don't want to get a functionality, it doesn't need to be a DSL modem, you want to study some signals and you only need an input starting from an RJ11 and going to a PC; what is the ...
1
vote
2answers
110 views

The math and the physics behind POTS phone lines

Since high school you learn something about Fourier Analysis and you can easily grasp the idea that a given signal that is variable over a given timeframe, is composed of multiple sub-signals with ...
1
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1answer
102 views

2/4 Wire Conversion Circuit For UK Telephone

I am currently trying to build an op-amp circuit which allows seperation of send and recieve signals from the UK telephone line (or a simulation of the telephone line). I am having difficulty ...
0
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0answers
60 views

Telephone “off-hook” indicator

I have a 2-line telephone that shows when a line is in-use (i.e. if an extension is picked-up, the indicator will light up on the phone). The two lines are being supplied via 1 RJ-11 cable (1 line on ...
0
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1answer
55 views

looking to capture an infared code

I am trying to get an infared signal being sent from an emitter (think along the lines of a remote control). I know I can use a fotoransistor on a breadboard to capture/detect the signal, but I have ...
0
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1answer
82 views

Patch-panel for phone splitter

I need a phone splitter (RJ11) to split 1 signal into 4 or more outputs. That's no problem, those can be bought in any store. But I was wondering if I can use a RJ45 cat6 patch-panel?
3
votes
2answers
91 views

Door phone audio signal to pc soundcard

I need to interface door phone system to a pc soundcard to listen and talk to the external unit. The door phone to interface is an as yc/200 of BPT and its a classic analog 4+n wires Door phone ...
0
votes
1answer
58 views

A voltage regulator that is controlling a voltage

My scenario is that I am having a circuit which having 12V as the input voltage and works beween 8V to 15V. I want to limit this circuit in a way that if the input voltage drops below 12V criuit ...
1
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1answer
116 views

Power a circuit and read output from tablet microphone port

I have a project that I'm currently powering with a AAA battery, providing 1.5v to a simple 555 timer circuit. The output of the circuit goes through a voltage divider into the microphone input of a ...
1
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2answers
222 views

Land line circuit suggestion / DTMF project

I am hoping to make a system that I can call in and using DTMF chip can control few things. I don't want to use a cell phone so it has to be a land line, however, it has to be automated so when the ...
10
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5answers
1k views

Control the hardware of an old phone using a Raspberry PI

I have a very old phone (60 years old) and I want to control its part using a Raspberry PI: Microphone & speaker from the head set The bell The dial wheel I have the electric circuit but don't ...
3
votes
1answer
121 views

telephone hold-on music

Can someone explain the following telephone hold-on music circuit in throughout manner because I am still learning how to simulate circuit using gnucap? When TR2 does not conduct, it switches off TR3 ...
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0answers
203 views

Using Java applet on a cheap Nokia phone to control Arduino via Bluetooth [closed]

I've built a nice wheel robot prototype with my kid. He had a broken R/C bigfoot truck: we've replaced its 'brains' with Arduino Pro Mini, DC motor drivers and HC-05 Bluetooth chip. Currently we ...
1
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2answers
88 views

Phone jack schematic and datasheet meaning

I am making an Eagle Cad library for this part, and I want to make sure I am making my part correctly. On this datasheet, http://www.switchcraft.com/Drawings/35rapc2av_cd.pdf, I am assuming that: ...
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1answer
150 views

Connecting phone using copper power wires

I want to install a video door phone (intercom) in my home, for this I have done a pre-wiring of 4 individual copper wires (normally used for home electricity) and the total length of wires is about ...
2
votes
2answers
274 views

POTS DAA circuit explanation

I am puzzling over this schematic, the datasheet just says to follow their recommendations exactly, and doesn't give explanation of the IC actions or circuit functions. The lower half is easy to ...
1
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1answer
50 views

Sampling phone line

I want to connect phone line to my PIC's ADC to sample signal changes without interfering the line. Human voice and DTMF signals are all under 4kHz level. So, I am hoping that any 18F PIC can do ...
0
votes
1answer
81 views

Connect 2 line phone to a 4 line system

There is a corporate phone system that uses multi-line phones. The idea is to connect a cheap 2 line phone only for answering calls without adding a line. Can this be done? Just connecting in ...
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3answers
166 views

Can a display landline phone instrument be made to work without a separate electrical connection

Since phone lines can supply power, there are landline phone instruments which work without a separate electrical connection. Typically these have no display etc. There are also those instruments ...
0
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2answers
89 views

What are these character sequences in connection with DTMF and a modem (telephony)?

I have a telephone, with which I dial a modem (analog, no ISDN) in order to send DTMF tones. If basically works, I receive something! For each key I press on the telephone I get a string like follows ...
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0answers
285 views

How can I isolate a short (in a mobile phone in this case)

I have a Nokia 6030 cell phone, and it's been serving me 7 years. It developed an interesting problem, which looks like a short of some kind: the battery drains very fast, for an hour or so, and the ...
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votes
1answer
1k views

Glitchy Touchscreen Caused by Charger [closed]

I recently bought a Nexus 4. I had a couple of spare chargers laying around. I used a charger that apparently had an issue exactly like: https://www.youtube.com/watch?v=mrpBTG0a6K8. If I used my own ...
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2answers
161 views

Calculator with phone keypad question [closed]

I am not an electronic person and found this site in a my quest for the perfect calculator. I use both a phone and calculator for calculations and find the back and forth to cause me to make errors ...
0
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1answer
133 views

Powering cell phone from arduino

I am a beginner in electronics and I want to ask you a simple question. Can I power my old SE w200i directly from arduino, using resistive divider like this one: ...
4
votes
3answers
557 views

How to draw current from a telephone line?

My landline phone comes with a lcd display caller id and clock. Even if I remove the 2 AA 1.5V batteries, the lcd still shows time even if I'm not busy on a call. The lcd has no other source of power ...
3
votes
3answers
171 views

Why is speech malformed when listening to a USB signal with an LSB receiver?

When you listen to an LSB (Lower Side Band) signal with your radio set to USB (Upper Side Band) or vice versa, the speech you hear is malformed. What causes this behaviour?
0
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1answer
155 views

Piggybacking ethernet/phone on Cat5e?

I've got a phone line on the blue pair, and VDSL on the brown pair. Leaving the orange and green pairs available. But when I try and connect a router in one room, and a laptop in the other room, I ...
0
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0answers
114 views

Erlang B telecom system (grade of service)

I am bit stuck with an answered question that I found online: We have an Erlang B system where the total number of served call is 15.48 erlangs. The system contains 23 circuits. The incoming calls ...
11
votes
1answer
543 views

Could someone help me understand this simple circuit?

This is a single-wire earth-return telephone system used in cave rescue communications. simulate this circuit – Schematic created using CircuitLab The ground is a metal casing to make ...
7
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2answers
2k views

How does a signal travel down a telephone wire?

To get data to a computer the telephone wire must sent a signal but how does it do it ? Does it use analogue or a digital signal? How does it send the "1s" and "0s"?
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votes
1answer
153 views

sniff telephone line data using old modem [closed]

i have an old modem that i'd like to use to sniff the data going out on the telephone line. i realize that i can't use the computers serial port to process the data as they are real slow. Can anyone ...
3
votes
1answer
994 views

Wiring a 1920s intercom to a contemporary door-entry phone

I have recently purchased a 1920s wall-mounted intercom: I would like to connect this unit to our existing "4+n" door entry phone system, replacing the cheap plastic handset that we currently use ...
2
votes
4answers
11k views

How to create a multi-extension intercom system using wired phones?

I want to create a simple (telephone based) intercom system in our new house. Shouting between rooms is not so good, and trying to use an IM client or Facetime doesn't have the immediacy of a good ...
1
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1answer
85 views

Insertion loss and Envelope Delay

Following diagram shows characteristics of typical telephone connection. (Insertion loss and Envelope Delay respectively) I have been able to understand, that plots are due to dispersive nature of ...
1
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2answers
149 views

Is telephone and LAN wiring symmetrical?

Is telephone and 10/100 MBps LAN wiring electrically symmetrical? I mean is it allowed to swap wires in the pairs, or is one of them like GND so they cannot be swapped? It's important to know when I ...