We look inside and power up the Apollo command module PCM Telemetry box, which provided the telemetry downlink for the Apollo missions. PCM stands for Pulse Code Modulation, and was entirely digital, in contrast to the analog FM telemetry prevalent at the time. Apollo Comms Playlist: https://www.youtube.com/watch?v=v49ucdZcx9s&list=PL-_93BVApb58SXL-BCv4rVHL-8GuC2WGb Links to schematics: …
From: Retro Roundup