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Understanding MFC R2 between PBX and

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  • #64639
    Luiz Salomon

    I’m trying to understand dialing in MFC-R2 (Register Signaling), and I can’t find any possible answer to my question.

    Let’s imagine this situation: I own a small enterprise with Direct Inward Dialing (DID), with 30 branches. I have a PBX that is installed in my company connected to a local switch thru an E1 that switches all the incoming calls. So far, so good.

    I know that voice is digitalized using A-law and sent in any of the 30 available channels of my E1. So far, still so good.

    Now, imagine a person picking up the phone to call a customer. When he picks up the phone, he gets a dial tone. This tone is generated by my PBX, after checking if one of my 30 channels is available. So far, so good.
    This person dials… and this is where my questions begins.
    The telephone generates DTMF’s in accordance to what number that person is dialing. For example, if that person dialed 555-1234, the telephone would generate for the number ‘5’ a 770+1336Hz tone. At this point,my question really arises: the PBX would send a 1740+1500Hz to the local switch. indicating the first number ‘5’. It keeps going to all other numbers, of course.

    I know that that there are all the signalings and etc right before and after it sends the number it wants to reach.

    My question is this one: if everything in an E1 is digital, how on earth do we have MFC? Where it happens? In what timeslot does it go? I read many times it goes on voice channel. Voice channel?

    If someone could please try to explain the dialing made by a PBX connected to a local switch using an E1, I would appreciate very, very much.

    Wallis Dudhnath

    MFC / R2 is a Register to Register signalling protocol.
    This was used with earlier Analog switches to send signalling
    over a CU (copper) pair circuit. The earlier decadic pulsing is now replaced bydual tones (MF). MFC / R2 can be used with E1.0 circuits,however, a MUX is required to groom the R2 signals for the E1.0 Time Slots. For your case with PBX you either use Earth or Loop Calling to seize a circuit. For use with a PBX R2 can be used. You have to configure the circuit for CAS.

    As the industry has moved on you will see that PBX/ISPBX/etc.. supports DASS2 / DPNSS1 / Q.Sig, etc..

    Centrex was also a solution where PABX functionality was provided from the Switch.

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