In the perfect CD-i setup your CD-i player is connected to a Philips amplifier/receiver that has a dedicated button for the CD-i audio channels - Interactive Dreams
Remote Control For Philips FR752/01X RC8080/01 FR751/00 FR731 FR732 FR731S/P01 FR752 Dolby Prologic Audio AV Receiver|Remote Controls| - AliExpress
Receiver Philips Fr-752 | MercadoLivre
Philips audio /video surround receiver FR751 with controller, Audio, Soundbars, Speakers & Amplifiers on Carousell
AV-receiver Philips FR 752 review and test
Remote Control For Philips FR752/01X RC8080/01 FR751/00 FR731 FR732 FR731S/P01 FR752 Dolby Prologic Audio AV Receiver|Remote Controls| - AliExpress