Com Key (sort of 1A2)

The AT&T Com Key 416 phone system was introduced in the mid-1970s, and was quite popular for about ten years. It had most of the features found in "1A2" phone systems, but did not require a central control unit (the big box on the wall officially known as the "KSU" or "Key Service Unit".)

All of the circuitry needed to operate up to eight phones with two lines and one intercom path was built-into one primary (or "master") phone. If a second primary phone was connected, system capacity could be doubled. Satellite (or "slave") phones provided the same features as master phones, but did not have any control circuits. A wall-mounting kit was available separately, for satellite phones only. Master phones have power cords and require AC outlets. Although up to 16 phones can be used in a system, there are only 10 intercom "addresses."

Com Key 416 phones are connected together with standard 25-pair cables. The phones were notable for their modular construction, which made it easy to replace defective components. Phones were made in ivory only, but faceplates were available in different colors, and faux wood finishes. Notable features (for the time) include a recall button (for fresh dialtone without hanging up), privacy with release, voice-announce intercom calling, two intercom paths, line-selectable electronic ringing, Direct Station Selection intercom buttons, conferencing, and monitor speaker.

Master phones were shipped from the factory for use on lines one and two, and intercom channel #1. In a system with two master phones, one could be modified to work on lines three and four, and intercom channel #2. Some of the circuitry inside the master phone looks like the 400D line card used in 1A2 systems. There is no electromechanical interrupter.

Special model phones provided features such as hands-free speakerphone. Additional circuitry could provide a fifth (private) line, and music-on-hold.

Standard button functions: