Datasheet for the MC145436A, a Motorola DTMF receiver that decodes telephone touch-tone dual-frequency signals into 4-bit codes.

Datasheet for the MT8870, a widely used DTMF receiver that decodes telephone keypad tones into a 4-bit code with a strobe output.

PDF datasheet covering the MT8880C, an integrated DTMF transceiver with a microprocessor bus interface, able both to decode and to generate dual-tone signalling.