MF (Multi Frequency)

A type of in-band signaling used on analog interoffice and 9-1-1 trunks.

Enhanced MF (Enhanced Multi-Frequency)

The Enhanced MF signaling protocol, used on the E9‑1‑1 tandem-to-PSAP interface, is based on the Feature Group D (FG-D) protocol and supports the delivery of up to two 10-digit numbers, the first of which is preceded by two ANI information digits (i.e., ANI “II” digits). Telcordia GR-2953-CORE

Note: combined two MF variants. Remove this note and change category to glossary when accepted