Questions tagged [telephone]
A telephone, is a telecommunications device that converts sound into electronic signals suitable for transmission via cables
222
questions
27
votes
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 ...
1
vote
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
votes
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
votes
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
vote
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
votes
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
votes
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
votes
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
votes
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
votes
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
votes
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 ...
0
votes
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 ...
0
votes
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
votes
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
votes
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
votes
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
votes
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
votes
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
votes
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
votes
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 (...
-2
votes
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
votes
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
vote
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?
1
vote
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)...
1
vote
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
votes
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
votes
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
vote
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 ...
1
vote
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
votes
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
votes
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 ...
1
vote
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
vote
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
votes
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%
...
1
vote
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 ...
1
vote
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.
-1
votes
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 ...
-1
votes
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
votes
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, ...
1
vote
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
votes
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
votes
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
votes
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.
...
