Editing Signaling (telecommunications) (section)

==Examples==
Every signaling system can be characterized along each of the above axes of classification. A few examples:
*[[DTMF]] is an in-band, channel-associated register signaling system. It is not compelled.
*[[Signalling System No. 7|SS7]] (e.g., TUP or ISUP) is an out-of-band, common-channel signaling system that incorporates both line and register signaling.
*[[Metering pulse]]s (depending on the country, these are 50&nbsp;Hz, 12&nbsp;kHz or 16&nbsp;kHz pulses sent by the exchange to [[payphones]] or metering boxes) are out-of-band (because they do not fall within the frequency range used by the telephony signal, which is 300 through 3400&nbsp;Hz) and channel-associated. They are generally regarded as line signaling, although this is open to debate.
*[[E and M signaling]] (E&M) is an out-of-band channel-associated signaling system. The base system is intended for line signaling, but if decadic pulses are used it can also convey register information. E&M line signaling is however usually paired with DTMF register signaling.
*By contrast, the L1 signaling system (which typically employs a 2280&nbsp;Hz tone of various durations) is an in-band channel-associated signaling system as was the SF [[2600 hertz]] system formerly used in the [[Bell System]].
*[[Loop start]], [[ground start]], reverse battery and revertive pulse systems are all DC, thus out of band, and all are channel-associated since the DC currents are on the talking wires.

Whereas common-channel signaling systems are out-of-band by definition, and in-band signaling systems are also necessarily channel-associated, the above metering pulse example demonstrates that there exist channel-associated signaling systems which are out-of-band.