All this talk about A lead control wiped away some cobwebs in the old brain. In the 1987 AT&T Premises Distribution Products Catalog, two A lead adapters were listed. The Z153CM adapter provided A lead control for a single line phone where there had formerly been a key telephone set. Like the regular 153 adapters, it consisted of a female amphenol with a modular jack for a single line phone, but there was a small circuit board in the hood. I recall that these were sold hanging up in blister packages in the AT&T Telephone Stores in the late 80’s and early 90’s.
The 354A adapter was similar except listed to provide A lead control for a two line phone or two single line phones used in conjunction with a 267C adapter.
Have not been able to find any additional information on these adapters on EBay or the internet other than the AT&T practice number for the Z153CM (461-099-006PS).
