FMVFT Frequency Modulated Voice Frequency Telegraph

FSVFT Frequency Shift Voice Frequency Telegraph

VFT Voice Frequency Telegraph

voice-frequency telegraph system

voice-frequency telegraph terminal

AM voice frequency carrier telegraph systme

VFCT Voice Frequency Carrier Telegraph

VFT Voice Frequency carrier telegraph Terminal

voice-frequency carrier telegraph

voice-frequency carrier telegraph equipment

voice-frequency carrier telegraph terminal

double Voice frequency signal

VF Voice Frequency

VFA Voice Frequency Amplifier

VFB Voice Frequency Generator

VFC Voice Frequency Cable

VFC Voice Frequency Carrier

VFC Voice Frequency Channel

VFCT Voice Frequency Carrier Terminal