I think the telephone earphone (he calls it a speaker) feeds both stereo amplifier inputs and is used for making the announcement.
Maybe he planned to replace the stereo amplifier he showed with an expensive siren with horn speaker and 2 channels amplifier.
Here is a cheap little siren module sold on all Chinese online sites. Another circuit must be designed to activate the siren for a couple of seconds when the phone rings. Then the phone calls about Duct Cleaning and Windows And Doors can wake his wife and his entire neighbourhood.
Will his wife hang up the phone?
i have connected and all working very loud but when at loud it have some fuzzy sound in it. If i can eliminate those fuzzy sounds then it perfect. I have connected the speaker phone wire to both channels of amplifier.The amplifier shown in post #1 is a stereo amplifier with what appears to be bridging type outputs. So either channel can drive the speaker, but not both. To use the phone it will probably be most effective to connect a small audio transformer across the earphone (speaker) in the handset and then use the other winding of the transformer to feed the amplifier input. Since the microphone is an electret it will have a DC bias and a much lower signal amplitude. That is why the speaker connection is a better choice.