APPLICATIONS
include: paging systems, repeater systems/mobile radio, interconnect dialers, PBX systems, computer systems, fax machines, pay telephones, credit card verification Figure 1 Pin Diagram Functional DESCRIPTION
M-8880 functions consist of a high-performance DTMF receiver with an internal gain setting amplifier and a DTMF generator that contains a tone burst counter for generating precise tone bursts and pauses. The call progress mode, when selected, allows the detection of call progress tones. A standard 6500/6800 series microprocessor interface allows access to an internal status register, two control registers, and two data registers. Input Configuration The input arrangement consists of a differential input operational amplifier and bias sources (VREF) for biasing the amplifier inputs at VDD/2. Provisions are made for the connection of a feedback resistor to the op-amp output (GS) for gain adjust- Tone bursts can be transmitted with precise timing by making use of the automatic tone burst mode.
Clare
