DESCRIPTION
The 75T204 is a complete Dual-Tone Multifrequency (DTMF) receiver that detects 16 standard digits. No front-end pre-filtering is needed. The only external components required are an inexpensive 3.58-MHz television “colorburst” crystal for frequency reference and a bias resistor. An Alternate Time Base (ATB)
is provided to permit operation of up to 10 75T204's from a single crystal. The 75T204 employs state-of
the-art "switched-capacitor" filter technology, resulting in approximately 40 poles of filtering, and digital circuitry on the same CMOS chip. The analog input signal is pre-processed by 60-Hz reject and band split filters and then zero-cross detected to provide AGC.

FEATURES
· Intended for applications with less requirements than the 75T202/75T203
· 14-pin plastic DIP or 16-pin SO package for high system density
· NO front-end band-splitting filters required
· Single low-tolerance 5-volt supply
· Detects all 16 standard DTMF digits.
· Uses an inexpensive 3.579545-MHz crystal
· Excellent speech immunity
· Output in 4-bit hexadecimal code
· Three-state outputs for microprocessor interface