I have successfully connected my Ring Doorbell Pro to a battery powered buzzer doorbell. I couldn’t find anything useful on the topic anywhere (other than a comment from Ring Support that it was not supported), but it’s actually pretty simple so I’m writing it up here in the hope that someone finds it useful.
I’m in the UK and the Ring Pro ships without the Pro Power Kit (see here). A quick online help-chat to the excellent Ring Support and they’d popped a free one in the post for me which arrived inside a week.
The Pro Power Kit is designed for American-style wired ding-dong doorbells. If you install a Ring doorbell in series with one of these bells, the doorbell breaks the circuit and so the Pro Power Kit is required to bypass the wired doorbell terminals and supply power to the Ring Pro. When the Ring Pro is pressed, the Pro Power Kit outputs a short burst of voltage across the two pins which ding-dongs the bell.
My Ring Pro is powered by a 24V AC plug-in transformer. All I did was connect the pins on the Pro Power Kit instead to a SPST 24VAC non-latching relay. Thus when the bell is rung, the voltage burst throws the relay closed for a short time. I wired the output throw of the relay into my battery-powered bell circuit, so my bell buzzes for the duration of the voltage burst. Simple but works well.
One additional point: in the Ring app, you can configure your external doorbell as either mechanical or digital. The only thing this setting does is changes the length of the voltage burst from the Power Kit. Mechanical is about half a second (think ‘ding-dong’). Digital lets you specify a number of seconds, so I can set my bell to buzz from 0.5 to 10 seconds (depending on how much I want to annoy the wife).
(Minor inconvenience, for full disclosure: whenever the transformer is powered up, the bell buzzes for about 15 seconds…)
Links to the accessories I’ve used:
Hope that’s helpful to someone!