Answering services, as known in the 1960s through the 1980s, earlier and slightly later, involved a business that specifically provided the service. Primarily, by using an off-premises extension (OPX) for each subscribing business, connected at a switchboard at the answering service business, the answering service would answer the otherwise unattended phones of the subscribing businesses with a live operator. The live operator could take messages or relay information, doing so with greater human interactivity than a mechanical answering machine. Although undoubtedly more costly (the human service, the cost of setting up and paying the phone company for the OPX on a monthly basis), it had the advantage of being more ready to respond to the unique needs of after-hours callers. The answering service operators also had the option of calling the client and alerting them to particularly important calls.
