Multi-frequency receiver

MFR-II Printed Circuit Card, circa 1985

The Mutli-Frequency Receiver (MFR) was a Digital Signal Processor (DSP) based printed circuit card designed by Mark A. Indovina at Computer Consoles Inc. in Rochester, NY. The initial MFR board, MFR-I, is notable for being designed in early 1983 prior to Texas Instruments officially announcing the TMS320C10 DSP April 8, 1983.

Variants

• MFR-I:
  • This printed circuit card, introduced in 1983, contained a single TMS320C10 16-bit fixed point DSP chip operating at 20 MHz.
• MFR-II:
  • This printed circuit card, introduced in 1985, contained two

TMS320C25 16-bit fixed point DSP chips operating at 40 MHz.

• MFR-III:
  • This printed circuit card contained a single TMS320C30 32-bit floating point DSP chips operating at 40 MHz. Although a prototype was designed, this card never went into volume production.

Features

• The MFR software, written entirely in TMS320 assembly language due to the poor efficiency of DSP C compilers at the time, was capable of decoding multiple channels of PCM digital audio.
  • MF, Multi-Frequency Tones
  • DTMF, Dual-Tone Band, Multi-Frequency Tones
  • Call Progress Tones
  • Other system audio frequencies as needed for on-line, and off-line system testing
• Due to the tight timing involved in the designs, controlled impedance printed circuit board design techniques was introduced with the MFR-I layout in 1983.