Questions tagged [telephone]

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

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How to connect a Battery Charging board / Management system, directly to a phones PCB to provide an alternative port for charging?

I have a Welcome phone (a no name phone) where I'm hoping to use the standard phone charging port for other uses. So I thought that I could solider a Battery Management system (BMS) directly to the ...
driver4567's user avatar
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Connect two old pulse-dialing phones

At work we have some old pulse-dialing (rotary) phones. We want to connect two of them to make a simple intercom. Whatever the number is composed (even one single digit) the other should ring and of ...
Mark's user avatar
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Why are old RJ-11 modular telephone cables reversed?

I've checked all my old modular phone cables and all of them have the terminal plugs attached so that the wiring is reversed. That is plug 1 is Black-Red-Green-Yellow and at the other end of the ...
Annette Gates's user avatar
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Intercom from old corded telephones

I'm experimenting with making a simple intercom from two old corded telephones. I'm including a buzzer and momentary switch on each end for an incoming call alert. Below is the circuit I made using ...
Annette Gates's user avatar
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1 answer
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Swapping a number pad from telephone to synth [closed]

I’ve recently acquired from the trash a toy synth keyboard piano. It works, but I wanted to create a stand-alone number pad from an old telephone. I’d like to know if it’s possible and how to do it if ...
Chris Zanillo's user avatar
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Hold button for UK Landline telephone

We have retro rotary telephones, and I'd like to make a hold button for the one in my office in the UK. This is literally a "ye olde rotary phone" (1940s) made from bakelite I have fairly ...
CompanyDroneFromSector7G's user avatar
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1 answer
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Capturing the output of a DTMF phone (without keypad access) [closed]

I wanted to make a gift for someone that uses a cheap DTMF phone as a controller. I thought I could just take it apart and rewire the keypad's ribbon cable but it turns out that the whole thing is ...
user358829's user avatar
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Connecting with a mobile phone over a 2-3 ft distance, and not beyond that

I have a device that I want to connect with a mobile phone at 2-4 ft, but not if the phone is further away than that. What signal or design can I use to accomplish that?
a nelson's user avatar
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2 answers
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What component could be

I have a VDSL telephony socket with some electronics in it. I reverse engineered the PCB, but there is one component I cannot identify at all. Look like a 0.25W TH resistor, light-blue body and a ...
Zoltán Gógucz's user avatar
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How to translate from voltage in a circuit to a command on a phone? [closed]

Basically, what I am trying to accomplish is getting my phone to make a call (to a specific number, say, my brother's), when a certain voltage threshold is exceeded. However, I have no clue how have ...
vac's user avatar
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15 W USB ports in car [closed]

My car has two 15 W USB C ports that will fast charge my phone, but they are not powerful enough to super fast 2.0 power my phone (S21+). Is there any kind of device that would take the two 15 W ...
Andrew Taub's user avatar
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How does a UK analogue telephone detect that the caller has hung up (disconnected)? [closed]

Scenario This is a question regarding the design of UK analogue telecommunications equipment and the consequent design impact that is necessary for a router duplicating those signals. It is asked so ...
user2834566's user avatar
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Can i safely use RJ11 and 24 guage wiring for hobby leds?

I would like to supply power to a bunch of LEDs (a dozen or so) on a model train layout. I would like each light to be modular, so I could easily unplug a building and replace it, etc. The LEDs are ...
nuggethead's user avatar
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What is the reason that this RJ11 cable can't be connected to this socket? [closed]

I connect one end of this RJ11 to my router's WAN port, and I connect the other end of it to a 3-pin plug, and I connect that 3-pin plug to the phone jack, but when I try to connect the RJ11 cable to ...
avdaad's user avatar
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What is this part in a “retro” phone?

I’ve got a recently manufactured “retro” landline phone that I wanted to scavenge some parts from, made in 2012 I think. I’d like to be able to do something with the ringer, which appears a lot ...
Rp Wav's user avatar
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8 votes
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Disable ring on land line phones

Years ago I bought a device at Radio Shack that disabled ringing on household phones. It was a very small box with a modular receptacle on one side, a pigtail on the other with a modular plug, and a ...
Roger's user avatar
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Solar lamp/phone charger output current too low for modern phones

I am building a solar lamp/phone charger following this page, with the circuit here below. I have two 18650 batteries in parallel. The charger module is the usual TP4056 taking 5 V input, and limited ...
mekano's user avatar
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2 votes
1 answer
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Three-wire old phone to RJ11

I'm trying to connect an old phone's three wires (white, red, green) to my home line VOIP-4-wire (black, red, green, yellow) but I don't know where or what to connect. I have read this: How to ...
jminhal's user avatar
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1 answer
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Phone battery charges linearly [closed]

I think this is probably a bit basic, but I've tried googling and have posted elsewhere. The question is vey simple. I've recently bought a new smartphone, with a standard lithium battery. Every other ...
JMyers11's user avatar
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3 answers
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Solve this puzzle: Car lighter port blowing phone battery [closed]

I brought my Jeep in for work, and the mechanic let it die. When he jumped it, he somehow blew my amplifier. He was able to fix that. A few days later, I plugged my phone into the car lighter port and ...
J M's user avatar
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Connecting 4P4C RJ9 Headset to 3.5mm pc port

I have a Plantronics CS520 Binaural headset that I'm trying to connect to my PC instead of a desk phone. I'm using a TRRS with T connected to speaker+, R disconnected, R connected to Mic, and S being ...
Mike's user avatar
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As a child I licked a landline telephone cord plugged into the wall

As a child I licked a landline telephone cord plugged into the wall.. It felt like it physically moved/shot me backwards.. Could this have happened or was it just a sensation from getting electrocuted?...
O-Grant's user avatar
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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: ...
Firat Dagkiran's user avatar
1 vote
1 answer
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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 ...
Alex Hajnal's user avatar
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-3 votes
2 answers
224 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 ...
riccs_0x's user avatar
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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 ...
Jake Dickerson's user avatar
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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 ...
mhmdghfr's user avatar
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2 answers
110 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 ...
Joey Martin's user avatar
1 vote
2 answers
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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 ...
questioner's user avatar
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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, ...
Tyler Durden's user avatar
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4 votes
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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 ...
Burt_Harris's user avatar
2 votes
2 answers
1k 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/...
edmeme's user avatar
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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 ...
Hackneyite's user avatar
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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 ...
The Riser's user avatar
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2 votes
2 answers
187 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 ...
InterLinked's user avatar
2 votes
2 answers
490 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 ...
Mike Brew's user avatar
3 votes
1 answer
693 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 ...
Zaki's user avatar
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1 vote
2 answers
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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 ...
Ben Longo's user avatar
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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 ...
NickG's user avatar
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31 votes
4 answers
6k 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 ...
across's user avatar
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1 vote
1 answer
511 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!
Darkkahn's user avatar
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1 answer
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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 ...
Kaswechiha's user avatar
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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 ...
Michel's user avatar
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6 votes
4 answers
4k 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 ...
Charley R.'s user avatar
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2 answers
3k 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 ...
Noob_Guy's user avatar
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0 answers
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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 ...
Ali's user avatar
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0 answers
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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 ...
Galactic's user avatar
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1 answer
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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 ...
mythbu's user avatar
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7 votes
6 answers
6k 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 ...
adamsfamily's user avatar
0 votes
3 answers
182 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 ...
Kurt Hikes's user avatar

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