Recording the entire signal of an RJ11 line

[vassock]

I need to record the entire signal of an RJ11 phone line, both in and out. I assume this sends a presumably digital signal including audio in, audio out, caller ID, etc... How do I do this? What do I record it to and how do I decode it later?

Note: I am NOT trying to just record the audio in/out from the RJ9 handset-to-phone line. That is fairly easy and cheap to do. I want the entire signal (which I presume is digital) which travels from the phone line to the telephone.

 

[davenn]

I want the entire signal (which I presume is digital)

its only digital if the phone is a digital phone like the type that use an IP connection to a server in a business system
if it is just a standard home phone then it will be analog


Dave

 

[davenn]

And ohhh BTW, illegal phone tapping can be treated as a court punishable offence in many countries

I would doubt you will find many people willing to risk their money or freedom


Dave

 

[Martaine2005]

Recording incoming calls, nuisance calls for evidence can be legal in certain circumstances.
Recording your own outgoing calls is legal if the third party are aware they are being recorded.
However, to automatically record incoming and outgoing calls without permission is an offence as Dave pointed out!
There are many ways to do it and many more ways to get caught!!
Why do you want to do this?
If you have a legitimate reason for doing so, the authorities will supply the equipment!..

Martin

 

[AnalogKid]

I assume this sends a presumably digital signal including audio in, audio out, caller ID, etc...
... I want the entire signal (which I presume is digital) which travels from the phone line to the telephone.

0 for 2. POTS (Plain Old Telephone Service) is essentially the same as in 1876, decades before the first electronic component (the vacuum tube) was invented. A telephone signal isn't just an analog signal, it is *the* analog signal. There is unidirectional power (-48 Vdc with a relatively high output impedance)), unidirectional signalling (90 Vac, 20 Hz), bidirectional audio (0.5 Vac sitting on approx. 8 Vdc of-hook), and bidirectional data (touch tones going out, caller id (Bell 202 modem) coming in, both riding on DC), all on one pair of wires that can run for miles without picking up excessive interference. All of the trunk stuff (station-to-station) is digital, but the line in your house is all analoggy. Wikipedia pages on the telephone and caller id have most of the tech details needed to build a bridging recorder interface.

The incoming and outgoing audio are separate at the handset, but duplexed (*not* multiplexed) in the phone line, separated/combined in a circuit called a hybrid. In old phones this is a 4 or 6 winding transformer, while electronic phones synthesize the function with opamps. Search for telephone hybrid schematic to see lotsa examples.

Caller ID data is sent to the phone between the first and second ring using the Bell 202 modem standard tones and modulation at 1200 bits per second. The signal rides on the -48 V on-hook loop voltage.

Ringing is a 90 Vac sinewave riding on the -48 Vdc loop voltage.

Touch-tones are called inband signalling because the tone frequencies are within the voice frequency bandwidth, 300 Hz to 3.5 kHz. At the phone set the tones are considerably louder than the voice audio signals.

ak

 

[davenn]

I should have closed this yesterday, before you responded AK