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

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1answer
40 views

Phone charger project [closed]

I have a question, how to make a led that changing light from red to green and when the led turn green a buzzer will trigger? I want to make a phone charger project, that when the phone fully charged ...
0
votes
1answer
60 views

Hardware reference design for a phone [closed]

I want to make a simple box with one button. Pressing the button will send a SMS Text message to a preprogrammed phone number. I have not designed a phone hardware before so looking for some simple ...
1
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1answer
58 views

What's the best phone cable for DSL? [closed]

I want to know what cable I should be using to connect my demarc to my DSL modem. When I plug in my DSL modem in the utility room (which is about 20' of wire from the demarc) I get a pathetic 4Mbps ...
1
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0answers
55 views

hijack project microtransformer doesn't work well

I am working on a project that need to get energy harvest from smartphone headset jack.I find hijack project has a solution.the energy harvest circuit of it is below: it use coilcraft transformer ...
0
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2answers
69 views

Power-line communication to household!

Most households in this planet have multiple 'wires' - one for plain electrical power, one for telephone, one for internet and one for cable TV (there may be more). I had heard of PLC ...
-1
votes
1answer
74 views

What is the minimum voltage requited to charge a cell phone? [closed]

When charging a cell phone, what is the minimum input voltage to the phone required not the battery directly, but the actual phone? Is it actually five volts that the wall charger puts out, or can it ...
3
votes
1answer
76 views

How to automatically test the audio quality of a telephone line that randomly goes bad?

I am a computer scientist and I'm working as sysadmin of a small firm where I've been managing also the telephone system that my predecessor put in place. Albeit I don't really have the skill set ...
0
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2answers
135 views

Landline listening

I still have a good old landline at home. But I miss the easiness of cell phones where you can just see a list of missed calls. I'm a MSP430 Launchpad hobbyist and I'm alway looking for some little ...
8
votes
1answer
1k views

Question about old telephones (late 70's - early 80's)

This question refers to old landline telephones that would have been used in households in Sweden in the late 70's and early 80's. I would think that this was probably similar to phone technology used ...
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2answers
62 views

Crosstalk vs interference

I don't even clear about the differences between crosstalk and interference. Could you explain me please? I just know that cross talk is the leakage power from other sources, whereas interference is ...
0
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2answers
168 views

5 volt generator

first time question, and not much of an electrical guy. so please be patient. My dad however, is an electrical engineer, who loves little goofy gadgets as most engineers do. For Christmas I want to ...
2
votes
0answers
94 views

simple GSM SIM modem

I'd like to build a prototype of simplest possible GSM device - a simple modem with SIM holder, capable of logging on to the SIM's provider network and nothing else. It's meant to be used as a GSM ...
2
votes
1answer
97 views

LCD connector repair [closed]

Does any one know if it is o.k to run a soldering iron over the connector with the fine black traces on in the photograph attached(or below I am new to pic posting :D)? I have an office kitted out ...
1
vote
1answer
84 views

Old phone continuity tester

An old man I used to work with had a set. Two old handsets with two conductors coming from them. It had a 9v power supply, I believe. We used it to trace existing interlock wires, hundreds in one ...
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votes
1answer
85 views

Audio amplifier not working after changing source (LM386L)

I have this simple amplifier here: I tested it with a regular PC audio jack input. Works fine. The problem is when I try to use it with a telephone (Panasonic KX-DT333, 2.5 mm jack). To be sure ...
0
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2answers
103 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 ...
1
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0answers
40 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
votes
1answer
93 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
votes
2answers
140 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
44 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
votes
3answers
404 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
votes
0answers
34 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
votes
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
votes
1answer
73 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
293 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 ...
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4answers
109 views

What is this electronics component?

What is the yellow component shown here? This is off a Outlet USB phone charger.
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votes
1answer
87 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
139 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
65 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
602 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
130 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
159 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
vote
1answer
212 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
votes
1answer
170 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
62 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
201 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
141 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
59 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
vote
1answer
143 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
vote
2answers
362 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 ...
11
votes
5answers
2k 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
148 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 ...
1
vote
0answers
316 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
vote
2answers
110 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: ...
0
votes
1answer
185 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
327 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
vote
1answer
56 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
92 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 ...
1
vote
3answers
274 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
votes
2answers
103 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 ...