Module dtmf 

DTMF (Dual-Tone Multi-Frequency) configuration and memory types.

DTMF is the tone signaling system used by touch-tone telephones and amateur radio for dialing, auto-patching, and remote control. The TH-D75 supports 10 DTMF memory channels (Menu No. 163) for storing digit sequences, plus 10 dedicated EchoLink memory channels (Menu No. 164), configurable encode speed, pause time, and TX hold behavior.

Per User Manual Chapter 11:

• Manual dialing: press [PTT] then press keypad keys to send DTMF tones in real time.
• Automatic dialer: store up to 16 digits per channel with an optional name (up to 16 characters). Transmit by pressing [PTT], then [ENT], selecting a channel, then [ENT] again.
• DTMF Hold (Menu No. 162): when enabled, the transmitter stays keyed for 2 seconds after each keypress without holding [PTT].
• DTMF Key Lock (Menu No. 961): locks DTMF keys to prevent accidental transmission while PTT is held.
• Encode speed (Menu No. 160): 50 / 100 / 150 ms per digit. Some repeaters may not respond correctly at fast speed.
• Pause time (Menu No. 161): 100-2000 ms between digit groups.

These types model DTMF settings from the TH-D75’s menu system (Chapter 11 of the user manual). Derived from the capability gap analysis features 128-132.

Structs

DtmfConfig

DTMF encoder and dialer configuration.

DtmfDigits

DTMF digit sequence (valid characters: 0-9, A-D, *, #).

DtmfMemory

A DTMF memory slot.

DtmfName

DTMF memory name (up to 8 characters).

DtmfSlot

DTMF memory slot index (0-15).

Enums

DtmfPause

DTMF pause time between digit groups.

DtmfSpeed

DTMF tone encode speed (Menu No. 160).

Functions

is_valid_dtmf

Returns true if the character is a valid DTMF digit.