Questions tagged [telephone]

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

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27
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4answers
5k views

How were four wires replaced with two wires in early telephones?

In this video, when A wanted to talk to B, a microphone was connected to a distant speaker using two wires (A → B). When B talked to A, a copy of above was used in the other direction (B → A) using ...
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1answer
87 views

Need help Identifying a resistor like component with orange and black bands

This component was on a telephone that was mistakingly connected to the mains rather than the phone line. Any help would be appreciated!
0
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1answer
24 views

Data rates for each user in ADSL with discrete multitone technique

I read about MODEM technology from Forouzan's 'Data Communications and Networking'. Under ADSL technology it was said- The modulation technique that has become standard for ADSL is called the discrete ...
0
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0answers
22 views

What the difference between a phone patch and a Subscribe Line Interface Circuit?

I'd like to construct a device that allows me to use my Western Electric 302 phone with a cellphone, plugged in via the trrs jack, and also have a circuit which allows me to ring the phone, and detect ...
1
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0answers
43 views

Leaky Bucket Example

I have an image below of a leaky bucket image that I am trying to understand for my telecommunications class, and I was hoping for some guidance/verification if my train of thought is on the right ...
5
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4answers
531 views

How was the first overseas phone call possible back in 1927?

I was watching the Peaky Blinders TV Series when something triggered my curiosity: If there were no satellites, nor underseas cables, how come the characters were making overseas phone calls? After ...
0
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2answers
123 views

How does ISP cut the customer's internet access technically?

We know that if we fail to pay our internet bill then our internet access will be cut. But how does the ISP technically cut the access? For wired internet, do they just shut down the port where the ...
0
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0answers
74 views

About live telephone line voltage

I have a question about the telephone line voltage. When I make a short for 12 volt I see the spark and heating, my question is why I can’t see anything (spark, heating) when I make short with the ...
0
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0answers
40 views

How could landline telephone service cause fire alarms to activate?

Someone I know informed me that their home’s fire alarm is occasionally triggered when he uses his home phone (landline). His alarm system company stated that they do not know why this occurs. They ...
0
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1answer
54 views

How does a “pulse dialer” (e.g. IN9151) internally work?

I'm wondering how a so called "pulse dialer" like the IN9151 (https://www.digchip.com/datasheets/parts/datasheet/237/IL9151-3N-pdf.php) internally works, meaning how it is achieved to ...
7
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5answers
3k views

Can lightning strike into the phone line damage electronics in the house through the ADSL modem?

I was always wondering about the following: If lightning strikes directly into the phone line outdoors, can the excess power coming from the phone line jump over the switching power supply of the ADSL ...
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3answers
62 views

How can you tell, remotely, if someone put their SIM card in a new phone? [closed]

On a recent television show, on ID Discovery, 'The Case that Haunts Me' (season 3 epi 4 'Cruel and Unusual') the lead detective finds out that the prime suspect has taken the SIM card out of his phone ...
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2answers
81 views

How to dial a phone number via DTMF tones?

I want to dial a phone number on a landline with DTMF tones generated by my phone. I tried soldering a 3.5mm audio jack to a phone cable and using my regular phone app, but nothing happened. In this ...
4
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0answers
177 views

Make old telephone ring

I recently found one of those old rotary dial telephones in my garage and amazingly it still is fully functional (I tested it by hooking it to the phone line). As I have no use for it as a telephone ...
0
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1answer
51 views

How to discharge a dead phone? [closed]

About a week ago I have taken my phone (s7 edge) off the charger, used it for about a minute, the phone turned itself off and the screen went black. I have tried turning it on, nudging the battery by ...
2
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1answer
180 views

Turn On Relay by Phone Line Power

I have two corded phone lines that I want to connect both of them to one telephone device. The phone must be connected to line 1 by default, and it switches to line 2 when it rings. I made a simple ...
-1
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1answer
94 views

Can phone flashlight damage my camera sensor

I have an s20 ultra and today i wanted to investigate on how are then cameras set up. So i got another phone and pointed it s flashlight to the s20 ultra cameras . The phone was closed. Did i damage ...
4
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2answers
168 views

Extracting speaker, microphone and hook signals from a two-line telephone

My aim I'd like to use a 'normal' telephone as an audio and switch interface for a project. I want to design a circuit that has the telephone A and B wires on one side (ie. an RJ-11 socket) and has ...
10
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4answers
89 views

Why are modern telephone lightning arrestors less prone to (rectification) RFI problems than old ones?

I was reading about telephone lightning arrestors in my ARRL RFI Book (first edition, copyright 1998), in chapter 9 "Telephone RFI" (by Pete Krieger, previously WA8KZH, now K8COM) and on page 9.6, the ...
3
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1answer
51 views

Details about Total Access Communication System (TACS)

I'm not sure if this is the right place to ask. I am trying to build a base station for a TACS (Total Access Communication System) phone, but I have not found any detailed document about it. The most ...
3
votes
1answer
219 views

Need help improving the Caller ID FSK demodulation circuit

I have a project for which I need to be able to read Caller ID from the telephone line. I found MT88E43B chip that does FSK demodulation. They have an application circuit in their datasheet (...
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1answer
140 views

Electric shock in water [closed]

In my country, someone died recently due to an electric shock when their smartphone fell in a bathtub. I'm trying to understand what's going on the charger side when a poor quality cable used to ...
0
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2answers
86 views

Slow usb charger for my smart phone? [closed]

I read that the optimal charger for smartphone batteries is 3.92v (to reduce degradation). Is it possible to implement a system that allows an external "charger" to cause charging to stop at this ...
1
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1answer
73 views

Number of voice channels for PSTN call

Does Public Switched Telephone Network (PSTN) use two voice channels for a single voice call - one for each direction?
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2answers
300 views

Is there any relation between LJU (Line Jack Unit) and broadband speed? [closed]

My question is about LJU (Line Jack Unit) aka Rosette. I am having BSNL (service provider company) copper line broadband in India. In spite of having wired broadband, I get speeds of 6Mbps(download)...
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1answer
75 views

Getting two way audio from/to a landline telephone, and making it ring

I have a "land line" telephone (ie. with an RJ11 plug) and a CSR8615 HFP bluetooth module (datasheet) — I'm looking to make my mobile's phone calls ring the land line phone, as well as being able to ...
0
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2answers
99 views

What misconception about telephone circuits are they trying to address?

I'm reading a book called "Telephony" published in 1905 (Miller,Mcmeen). The book starts with this quote: To properly understand the manner in which sound is transmitted from one end of an ...
0
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1answer
45 views

How does a video entry system send audio and video, as well as ring/unlock over 4 wires?

I’ve been trying to understand how my door entry system works. Between the monitor/base station and the bell/camera/speaker there’s only 4 wires: 12V DC GND Voice (2 way) Video (1 way) I opened it ...
1
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1answer
449 views

Can I extend a single twisted pair DSL line using a coaxial cable?

I'm in the process of setting up a DSL modem/wifi router, which should be connected to a phone line that uses a single twisted pair. However, the phone line enters my house in a slightly inconvenient ...
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0answers
95 views

Are the two wires in a telephone cable swappable?

I am in Switzerland. Our landline is delivered through an unshielded twisted pair cable. Are the wires in the pair swappable ? Or does it have a polarity ? The lines is supposed to provide ADSL ...
-1
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1answer
43 views

Power consumption [duplicate]

A phone charger is rated with input of AC 240v 50/60Hz 0.35 amps will it accept only 240 v 0.35 or will it take full 240 v 16 amps and step it down please I am very new to electrical stuff please help ...
3
votes
2answers
93 views

Spiral hoar frost and spiral device around telephone or electric landlines

I live in Germany. When I travel by train, sometimes there are cables that run from pole to pole parallel to the train track. From the lack of insulation between wire and pole, I guess these are ...
0
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1answer
96 views

SIM to RJ: emulating SIM card as a RJ connector [closed]

i recently got in a Goodwill store one of the 2500 model phones https://en.wikipedia.org/wiki/Model_500_telephone#Model_2500 and i want to use it. the problem is that i don't have a phone line in my ...
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1answer
173 views

Detect phone call termination

I am designing an automated telephone circuit that will work with the PSTN line. I already had a question to detect the incoming ring signal. Now I want to detect whether the opponent person in the ...
5
votes
4answers
9k views

CAT5 for telephony

I wish to extend my incoming telephone connection using CAT5 as I've heard it could provide better performance than standard single stranded telephone wire over long distances. There are only two ...
1
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4answers
169 views

TDMA in telephone circuit switching - isn't there delay in transmitting a particular user's speech? [closed]

Let's do a simple case on the left with X and A user telephones. So the way an analog signal (user's speech X) is handled, is that it is sampled at 8000 bits / sec. The high-speed C-channel has 128 ...
0
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1answer
102 views

600 ohm modem transformer impedance calculation by formula

From the datasheet of a modem transformer we have: Impedance, Primary: 600 Ω Typ. @ 1 kHz 1 Vrms* Shunt Inductance Lp, Primary: 3.2 H min. @ 1 kHz D.C. resistance @20°C: Primary = 82 Ω ± 15% ...
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4answers
94 views

Which capacity measurement is the correct way to measure?

So I've seen batteries showing their capacity in mAh and I've seen others showing in Wh. Phone batteries are always measured in mAh, while for some reason BatteryInfoViewer on my computer only shows ...
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0answers
145 views

Why telephone lines use -48V not +48V? What’s the difference practically in -ve and +ve voltages? [duplicate]

Why telephone lines use -48V not +48V? What’s the difference practically in -ve and +ve voltages? Detailed answer would be appreciated.
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1answer
328 views

Is it legal to use electricity from a phone line?

I saw a video by ElectroBOOM where he wiretapped his home phone. So, apparently, there is around 40v coming through the phone line, with higher peaks when it rings etc. I have a few questions about ...
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2answers
117 views

General questions about the telephone line a.k.a “last mile” [closed]

Before the digital data gets conveyed over the "last mile", it passes a modem, which converts this digital data into audio signals (Which is often called analog) (but the binary system still is there, ...
0
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1answer
54 views

3x AA battery phone charger input voltage drop

I am using a 0.9-5 V to 5 V dc-dc step up converter to charge a phone using 3 AA batteries, but whenever I plug in the phone it starts charging but the input voltage drops from ~4.5 V to less than 2 V ...
2
votes
2answers
152 views

How are severed phone lines, the ones on utility poles, repaired when they are severed

I have been searching for this answer for a long time and I haven't found any info on the way severed lines are repaired. There must be tens of thousands of tiny wires that must reconnected, and in ...
3
votes
3answers
2k views

Analog (POTS) telephone off-hook detection

With a single POTS telephone line and two or more handsets, when a call comes in, each handset can join in with the call. This can sometimes be an issue when one user doesn't know the line is in use, ...
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3answers
3k views

How does this old telephone ringer work?

I bought an old rotary phone with the hopes of cannibalizing it for a doorbell/intercom thing in my apartment building. It looks absolutely marvelous inside: However, I'm having trouble figuring out ...
0
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1answer
10k views

Using a usb-c laptop charger to charge a phone [closed]

I don't really know anything about electronics and I'm not sure if it's the right place to ask, but still. Is it OK to charge my phone with my laptop's charger? Here's info on the laptop charger: ...
11
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3answers
3k views

How does the telephone's keypad work?

I disassembled some old telephone and mobile phone. Every keypad is different, and yet, all of them have those "spirals" (see the image below) under the button or something similar. What I don't ...
0
votes
1answer
579 views

Fast charging 2.0: 7V×2.5A, 9V×2A or 12V×1.5A?

The FastCharge 2.0 standard has these charging specifications in the exact same charger (a VoltCraft car charger): 5 V up to 2.0 A (10 W max.) 7 V up to 2.5 A (17.5 W max.) 9 V up to 2.0 A (18 W ...
4
votes
5answers
205 views

How well does telephone delay correlate to geographic distance?

I have a friend who lives on the other side of the world, and every time we speak over the phone, there's roughly a second of delay between one of us saying something and the other hearing it. I've ...
24
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4answers
5k views

Why do push button telephones use dual-tone for signalling?

Here is a related information from wikipedia: For touchtone service, the signal is a dual-tone multi-frequency signaling tone consisting of two simultaneous pure tone sinusoidal frequencies. ...

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