YouTube - DMS-100 Startup and First Phone Calls on 2023-02-25 by Joe's VAX Repair and More. See also DMS-100.net.
YouTube - DMS Decomm on 2018-08-19 by Ken Pickering.
AT&T long lines:
YouTube - Last Crossbar Telephone Switch (Central Office) In The 2022 PSTN (TESLA UK11 PBX) on 2022-12-24 by suriva.