R2 Signalling - MF Tones

MF Tones

One unifying aspect of R2 register signalling variants is that all audio tones are combinations of two frequencies. Each pair of two frequencies is called a multi-frequency tone, or MF tone. Each call attempt has an origination end and a termination end, both to the multi-span call as well as for each span within that multi-span call routing. The origination end is called the outgoing register in R2 parlance. The termination end is called the incoming register in R2 parlance. The outgoing register transmits forward MF tones to the incoming register. The incoming register transmits backward MF tones to the outgoing register. The outgoing register detects backward MF tones arriving from the incoming register. The incoming register detects forward MF tones arriving from the outgoing register. The outgoing register transmits the first signal, but from that point forward the outgoing register merely passively responds to the prompting driven by each signal transmitted by the incoming register. (In apt modern-era proleptic terms, the outgoing register's first push signal to the incoming register is similar to a peer-to-peer message, whereas the incoming register's pull signals, which request information from the outgoing register, are client–server, where the client is the incoming register and the server is the outgoing register.)