Part 1 https://www.youtube.com/watch?v=ucI0uiQhaw4 patreon.com/user?u=65542787 https://www.paypal.com/donate?campaign_id=EKFVL6Q5QBU2N This is a two-part video, covering the 1 A series, phones and key telephone units. Also the 400 series connected to a 1A1 type system . The early 1 A systems had an option of no lamps in the phones, a very cheap and dirty approach to multi line phone system.