UDS Universal Data Systems/Motorola Model 201B/C MB M Modem
Year First Appeared
1984
Creator
Unknown
A Bell‑compatible 2400 bps modem that operates as a 201B on leased lines and as a 201C on the public switched telephone network, supporting synchronous or asynchronous data via DPSK modulation and featuring built‑in diagnostics.
Importance in Internet Culture
2400 bps Bell 201‑class links were the workhorses of corporate data networks, tying terminals to hosts over leased and dial lines and enabling early dial‑up access long before TCP/IP was commonplace. Systems like the 201B/C bridged private lines and the PSTN, seeding the habits, and the infrastructure, that later scaled into the early online and pre‑Web culture.
Interesting Fact
The 201BC/AS front panel used a multi‑position rotary switch to invoke built‑in local and remote diagnostic tests, and nine status LEDs to report conditions, letting operators run end‑to‑end checks without external test gear. The same card could also be fitted into UDS’s RM‑116 shelf, so the standalone “MB” unit and rack module shared the exact modem electronics.