Blue is abbreviated Bl
Black is abbreviated Bk
Brown is abbreviated Br
Thank you for replying, Arthur,
You're welcome
...your BSP does shed some light but still doesn't answer my basic thoughts on all this.
You basic question was, why or how is the speakerphone connected directly into the phone, and my answer was, the BSP doesn't allow that method, but it will work. The way your phone is hooked up is non-standard. The BSP cannot address situations that might occur, only situations that must occur. The BSP's are prescriptive. That seems to address your thoughts.
I guess it makes sense that there must have been some type of connection plan for the Type 3 speakerphone as it was still extant when the 2565 was introduced.
Correct. That's what the BSP in my link exactly describes. It shows the use of the 66E terminal and the 149-type connecting block. The 2565 is just the TT version of the 565 which was around a long time. The introduction of the 156x and 256x did not affect the distribution of the 3-type speakerphone.
I always thought however, that the 2565 was introduced to make the 4A speakerphone a "plug and play" operation.
No, the x565 sets, as opposed to the x564 sets, were simply phones that existed in the arsenal of sets that could be requisitioned for specific tasks. x564 for applications without speakerphone, and x565 for installations with speakerphone.
(Was the 2564 just pre-4A or just no speakerphone..period?)
See above answer. They were installed per the features that were ordered by the subscriber.
I think your confusion may lie in the fact that 3-type speakerphones, 4-type speakerphones, rotary key sets and Touch Tone sets, and sets with and without the extra leads for speakerphone service, all appeared in the same era, and they crossed over in the production timeline. There is no cause and effect among their appearance. If a subscriber had a defective 3-type, the repairman was expected to repair or replace the defective components, even after the 3-type was rated "MD" (manufacture discontinued).