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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