Questions tagged [telephone]

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

Filter by
Sorted by
Tagged with
0 votes
1 answer
76 views

Analog telephone circuit and TEA1062 [closed]

I am currently working on an analog telephone project. I have some questions. ICs and Central are below: Central: KX-NS500 (gives 28VDC) DTMF receiver: MT8870 DTMF generator: HT9200B MCU: ...
user avatar
-1 votes
0 answers
59 views

Signaling on a medium with more than one frequency at once?

Does anyone know how it’s possible to have different carrier frequencies in a medium like copper cable and separate the original signals at the receiver? For instance, looking at image A below, this ...
user avatar
  • 329
1 vote
1 answer
50 views

Choosing a replacement electret microphone

I'm trying to select a suitable replacement electret microphone for an analog (POTS) phone. The existing electret is completely unmarked so I don't know its part number or parameters. I'm not well ...
user avatar
  • 1,306
-3 votes
2 answers
210 views

5G and aircraft? [closed]

I just read the statement of a company, "We are frustrated by the FAA’s inability to do what nearly 40 countries have done, which is to safely deploy 5G technology without disrupting aviation ...
user avatar
  • 510
0 votes
1 answer
97 views

Driving two bell coils from an old phone with 90 V, 20 Hz AC

I have an old phone which stopped making calls, but the ringer still worked. I used a phone ring generator that generates 90 V, 20 Hz AC to test this. I want to place this ring generator inside the ...
user avatar
0 votes
0 answers
61 views

Telephone headset adaptor weak microphone and speaker sound

I have made a simple adaptor for a telephone P4C4 -- RJ9 -- separate headset output (The wiring diagram of a telephone handset can be viewed in this wikipedia article) to two TRS jack for an ordinary ...
user avatar
0 votes
2 answers
97 views

Make a faux call on old 1950s touch tone phone [closed]

I have a 1950s ice cream shop and just bought a vintage touch tone phone. It works if I connect it to a phone line but I won't be doing this. What I really want to do is pre-record messages that will ...
user avatar
1 vote
2 answers
855 views

What does GSM 900/1800 mean?

I was looking at old Nokia 3310 phones, which have GSM 900/1800. I did some research online from a government website, along with some Google searches, to understand what GSM 900/1800 means. I got a ...
user avatar
0 votes
4 answers
162 views

How did phone networks do switching in the days before programmable ICs?

How did phone companies and companies that made PBX's do switching with discrete logic or simple, non-programmable ICs? The caller would type in a number, so the system is receiving a sequential code, ...
user avatar
  • 2,128
4 votes
7 answers
2k views

What do you call the yellow and black conductors in domestic telephone wire?

Any wannabe telco guy can tell you that the green and red pair are called "tip" and "ring" respectively, most can tell you the historical reason why. That's not what I'm looking ...
user avatar
1 vote
1 answer
139 views

Replacing phone battery with power supply

I have an old phone (nexus 5) that I want to use for a project. I need to replace the battery with a permanent power supply, I've found the 3 pins of the battery and made a breakout connection with 1/...
user avatar
  • 31
0 votes
1 answer
42 views

identification SMD 3 Pin 3x1.5mm code 4B C39 for stereo camera

I am trying to build stereo camera using android or iphones. The pcb is from a wired selfie stick and works well. By using 2 pcb's with one push button, simultaneous photos can be taken. I have looked ...
user avatar
0 votes
0 answers
49 views

Two phone batteries connected in series not working

I have two, fully charged, 3.7V standard Nokia phone batteries, that I want to connect together to use as a 7.4V battery, I connected the (+) of one to the (-) of the other, and then tested it but it ...
user avatar
2 votes
2 answers
115 views

Is it safe to wire a telephone to a breadboard?

I am trying to connect a hardwired 2554 telephone set. There's only a few inches of slack wire coming out of the phone since it appears it was just cut there. I managed to get about half an inch of ...
user avatar
2 votes
2 answers
162 views

Convert 60V AC 50Hz to 60V AC 25Hz

The setup is a 240V 50Hz AC transformer outputting 60V 50Hz AC. Connect this power supply (with a push button) to an old telephone and it rings the bell on command, but unrealistically fast. I need to ...
user avatar
3 votes
1 answer
418 views

How does this telephone circuit eliminate the sidetone?

I know that the sidetone in telephones is removed by a hybrid transformer or by differential amplifier using an op-amp. I don't know how this circuit does the job using just 2 transistors (I took the ...
user avatar
  • 35
1 vote
2 answers
129 views

Providing phone line current for direct modem-modem communication

In order to directly connect two modems without a real phone line, one option is to put a battery inline (to create the current loop?). Most information I've found about this relates to the SEGA ...
user avatar
  • 111
0 votes
1 answer
295 views

Is GSM full-duplex?

GSM uses FDD (frequency division duplexing) and provides separate channels for uplink and downlink. I found however, in this link, that the mobile station does not receive and transmit at the same ...
user avatar
  • 363
28 votes
4 answers
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 ...
user avatar
  • 1,070
1 vote
1 answer
177 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!
user avatar
0 votes
1 answer
36 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 ...
user avatar
1 vote
0 answers
47 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 ...
user avatar
  • 187
5 votes
4 answers
1k 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 ...
user avatar
0 votes
2 answers
457 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 ...
user avatar
  • 377
0 votes
0 answers
79 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 ...
user avatar
  • 1
0 votes
0 answers
47 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 ...
user avatar
  • 101
0 votes
1 answer
58 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 ...
user avatar
  • 157
7 votes
6 answers
4k 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 ...
user avatar
0 votes
3 answers
72 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 ...
user avatar
0 votes
2 answers
272 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 ...
user avatar
8 votes
2 answers
2k 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 ...
user avatar
0 votes
1 answer
70 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 ...
user avatar
2 votes
1 answer
499 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 ...
user avatar
  • 277
-1 votes
1 answer
409 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 ...
user avatar
4 votes
2 answers
444 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 ...
user avatar
  • 562
10 votes
4 answers
164 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 ...
user avatar
3 votes
1 answer
61 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 ...
user avatar
3 votes
1 answer
349 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 (...
user avatar
  • 81
-2 votes
1 answer
144 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 ...
user avatar
  • 177
0 votes
2 answers
103 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 ...
user avatar
2 votes
1 answer
156 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?
user avatar
  • 257
1 vote
2 answers
427 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)...
user avatar
  • 111
1 vote
1 answer
93 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 ...
user avatar
  • 562
0 votes
2 answers
103 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 ...
user avatar
0 votes
1 answer
52 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 ...
user avatar
1 vote
2 answers
718 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 ...
user avatar
  • 121
1 vote
0 answers
217 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 ...
user avatar
  • 5,743
-1 votes
1 answer
44 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 ...
user avatar
3 votes
2 answers
133 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 ...
user avatar
0 votes
1 answer
126 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 ...
user avatar

1
2 3 4 5