The PacBell branding suggests this unit hasn't been converted, but most popular payphone model have a COCOT conversion kit available. COCOTs or customer-owned-c

The PacBell branding suggests this unit hasn't been converted, but most popular payphone model have a COCOT conversion kit available. COCOTs or customer-owned-coin-operated-telephones perform the charging internally and don't require exchange support, so they're a lot simpler to get working. The conversion kits are pretty readily available because a good majority of payphones out in the world today, even operated by the incumbent telco, are actually COCOTs since they've become cheaper and easier to manage over time. Plus a lot of payphones aren't managed by the telco anymore but instead by a separate private company like PTS, which runs all COCOTs with an arrangement where they "dial in" to a management system regularly for configuration and reports. General rule of thumb is that any payphone that accepts credit cards is actually a COCOT, any payphone not branded by the ILEC is a COCOT, and a lot of the rest are COCOTs too depending on the telco. "Genuine" exchange-controlled payphones (that signal coin drops back to the exchange) have become rare. I'm pretty surprised he went with the Viking box actually because it costs more than an inexpensive FXS ATA, and a lot more than getting an ATA used. It's simpler to set up, but on the other hand some ATAs have internal logic to connect their two lines that you can enable so they behave as standalone devices. I think this is typical on the older Ciscos.