Overview

The LC737212 and LC737212M are CMOS LSI telephone dialers for pushbutton telephones. They support both DTMF and pulse dialing. These products include 25 16-digit memories for storing telephone numbers and one 63-digit memory for redialing, and they provide, in a single chip, all the functions required for dialing and control for a standard independent telephone, including on-hook dialing and a hold function. They also provide a serial I/O interface for connection to a microcontroller.

Functions

• Fabrication in a CMOS process that allows these circuits to be directly operated from a telephone line

• Support for single-contact keypads

• Built-in oscillator circuit (fosc = 3.58 MHz) that can drive either a standard color-TV crystal oscillator element or a ceramic resonator

• High-precision DTMF signal

• Frequency generator circuit (±0.1) adopted for eased ceramic resonator selection

• Five one-touch 16-digit auto-dial memories and 20 quick-dialing memories

• On-hook or off-hook can be specified for memory entries.

• Mode change and pause data items can be stored in the dialing memories.

• 63-digit redial memory

• Automatic pause (3.9 seconds) insertion when the mode is switched.

• Automatic pause (1.0 second) insertion after a flash operation.

• Mode changing is one-directional, from pulse mode to tone mode.

• Output of a key press tone (1036 Hz, 31 ms) for keys other than DTMF keys when key input is valid

• Output of an operation complete confirmation tone (2072 Hz, 279 ms for each telephone number) when a telephone number is stored in memory

• Generates 12 signal types in DTMF mode.

• Supports an on-hook dialing mode.

• Supports a hold function with hold mode.

• Supports both 10 and 20 pps dialing pulse rates.

• The mode can be switched from either the P/T pin or by a key input.

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