Telephone (Engaged)

[paulh53]

Hi chaps/chapesses

Does anyone know how I Can build a "Telephone Engaged" Indicator?
I need to have some kind of indication to let me know when the kids are "On or Off" the phone or internet when they are upstairs, I don't want to run up & down stairs every 5 minutes to ask them, And I don't want to be picking up the phone to check if it's engaged, Specially if they are whispering "sweet nothings" to their loved ones,
Ideally this "Indicator" would need to be an "LED" which would come on when the phone line becomes "Engaged"
Perhaps manufacturers should put this form of "Indicator" on all of their phones
But I would be quite happy with just an LED Indicator

Can't wait for some replies

 

[Handyman]

1) If you were only concerned with endless chatting, then buy a digital cordless phone, and put the base unit downstairs. When they use the phone, a light on the base unit comes on to tell you it's in use. Also, from time to time, the battery will run down, and they will have to come downstairs and put the handset back on the base unit to charge, so you might see your kids more often and they might remember who pays the bill.

2) Consider installing a second line. I had same problem and gave up in the end and installed second line. Costly, may be, but what a saving in hassle over 15 years of teenage children all trying to talk and surf simultaneously.

3) When you pick up the phone to see if it's in use, pause for a while before putting the receiver down (whether you listen or not is a matter for your own conscience). However, your kids will hear the click, and be unsure if your listening. After a while, they will have to come down to see if you are listening in. Eventually, they will tire of this and might reconsider their extended use of the phone.

 

[yankey-sparky]

What you're looking for is called an "extention in use indicator" or "line in use indicator", and they're not uncommon in electronics shops in the US and many places that sell telephones. You might want to call around, they're easy to install.

However, if you really do want to build one yourself, it's a reletively simple circuit. A couple op-amps, one transistor, a few diodes, and a handful of resisters. You can find plans on the internet and also in hobby electronics books.

Do UK phone lines run on 48V DC like they do in the US?

 

[breezer]

Do UK phone lines run on 48V DC like they do in the US?

50 or 35 depending who supplies your line

 

[yankey-sparky]

Do UK phone lines run on 48V DC like they do in the US?

50 or 35 depending who supplies your line

This may be a bit more complicated then. As I understand the circuit, it detects the 10V drop in voltage on your line when a phone is in use, and uses that to tell you when an extention is in use.

If you've got these indicators in the UK, which I suspect you do, there may be two different versions for the two different voltages. I don't see any reason the plans for the US build-it-yourself version wouldn't work on the 50V UK line, but it would probably require modification for a 35V line depending on how far the voltage drops when a phone is in use.

Which would be an interesting challenge...

 

[breezer]

to be honest , never heard of them, but then again, ive not looked

 

[securespark]

Have looked through my specialist telecoms supplies catalogue for an in use indicator, but cannot find one.

Better than the suggestion to get a second line would be a piece of kit called BT twin talk.

I don't know the costs involved in running this system, but you need to subscribe to BT Callsign service. You then have two numbers associated with your one line and this kit allows you to route calls to a certain number through a certain phone. Presumably, the calls are split on the bill, ie £W for X number, and £Y for Z number.

The hardware costs £20 trade ex vat.

Of course, it may not work with another suppliers system........

 

[yankey-sparky]

Since nobody seems to have ever heard of these things...

TEC Phone in use indicator unit

Build-it-yourself phone in use indicator circuit

The hobby circuit is, of course, only one of several available in various internet sites and electronics books. This is the simplest one I've seen.

I make NO guarantees that either of these will work in a UK phone line.

 

[hsiboy]

tandy used to sell them.

As far as that circuit of bills goes, its a bit ott. one thyristor an led and a resistor will do. which is whats inside of the tandy ones. of course tandy is rip, but there was a company doing mail order in the uk for tandy products (radio shack in the US).

Lat time i saw one of those things was at one of those electrical tat stalls at the local market, cost about £3.

looks like a normal two way phone splitter, with only one socket, and an led where the other would normally be.

Stuart.

P.S Breezer where do you get your figures?? yanky-sparky, yes 48v dc.

 

[breezer]

P.S Breezer where do you get your figures?? yanky-sparky, yes 48v dc.

from the phone lines i work on.

 

[securespark]

The voltage that leaves the exchange is 50V, but it will drop the further you are away from the exchange, hence variations. However it is always a good idea to assume 50V wherever the line is situated in relation to the exchange. We assume 240 for maibs related stuff, but I've had as low as 232 and as high as 251 V .

 

[NEO]

Change the internet connection to DSL. This uses digital demodulation and does not interfere with the analogue signal you receive during a phone call (Speech)......therefore phone and internet can run simultaneously

N.B - Internet fee may increase slightly (depending on ISP)

 

[AdamW]

Change the internet connection to DSL. This uses digital demodulation and does not interfere with the analogue signal you receive during a phone call (Speech)......therefore phone and internet can run simultaneously

N.B - Internet fee may increase slightly (depending on ISP)

Here is a chance to show my true geek colours (cracks knuckles): DSL doesn't interfere with voice calls because it uses a higher frequency. The international standard phone channel (the DS0) samples at a rate of 8Khz with an amplitude resolution of 8bits. If you remember your Nyquist theorem this does of course mean that the line is good for up to 4KHz which is perfectly good for voice conversation. A DSL (specifically an RADSL connection, most common in the UK) works in a band from around 64KHz to 1.1MHz. This is why it can work alongside the voice conversations. Just think of it like radio, where you have lots of channels that don't interfere with each other.

Now all I have to do is convince Argos to stop putting "digital ready" next to every bit of electrical kit they sell and I can rest knowing the world is a better place.

 

[DavidArthur]

Tiscali doing DSL 150Kbps for £15.99 per month free modem and connection.

Good deal I think


Dave