"The TF2300A is a modulation meter from Marconi. Modulation meters measure degrees of modulation in a modulated signal.","Additional Features:","The Marconi Instruments TF2300A FM\/AM Modulation Meter measures FM deviation up to 500 kHz, Carrier frequency range: 4 to 1 GHz, usable up to 1.6 GHz with internal oscillator; Measures AM depth up to 95% at carrier frequencies up to 350 MHz; Modular construction with all solid-state active elements giving maximum reliability. The Marconi TF2300A basically comprises a low-sensitivity superheterodyne receiver having very linear (switched selected ) f.m. and a.m. demodulators. The demodulated signal is amplified, rectified, and applied to a panel meter which is calibrated directly in kHz peak deviation and per cent modulation depth as appropriate."