Here's a prototype keyboard adapter for the PS1. It was intended to be used with the planned modem. Sony did create an official version without the cord, but was never released. :
raphnet. - SNES Controller to PSX adapter
OSTENT PS1 PS2 to PC Computer USB 2.0 Controller Adapter Converter for Sony PS2 Wired Controller
Adapter - PSX Y-Connector | Flo-Dynamics
8BitMods - SONY PlayStation 1 adapter for HD Retrovision MD2 / Genesis 2 cable
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Amazon.com: AC Power Supply + Audio Video RCA AV Cable Adapter Cord To External TV Screen Monitor For Sony Playstation 1 2 3 PS1 PS2 PS3 PSX Original FAT Gaming Systems Console
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4 Player Multi Tap Adapter PS1 - Official Sony Brand - Gaming Restored
Buy PSX to SS Sega Saturn Controller Converter Adapter - Golden Shop
Amazon.com: OSTENT PS1 PS2 to PC Computer USB 2.0 Controller Adapter Converter for Sony PS2 Wired Controller : Video Games
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