What system established the premise of directing incoming calls based on predetermined instructions?

Answer

Automatic Call Distributor (ACD)

The Automatic Call Distributor (ACD) is identified as the earliest recognizable precursor to modern routing logic. Its function was to establish the essential premise of call routing: taking an incoming call and directing it to one destination selected from many available agents or lines. This selection process was governed by a set of predetermined instructions, formalizing the core requirement to map an incoming signal to an appropriate outbound path using defined, albeit simple, rules. This foundational structure enabled all subsequent, more sophisticated algorithms to be developed upon it.

What system established the premise of directing incoming calls based on predetermined instructions?
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