My dad is having difficulty hearing his cordless phone ring in his shop, due to ambient noise. He has the phone connected to a Straight Talk home phone service device. So, there is no legacy analog line. I am trying to drive an external ringer that was built for an analog system. The Straight Talk jacks do not output sufficient current to drive the ringer.
Is there a way I could use a ring detector and relay? Does anything exist? How difficult would building something be? I have read that the old ringers require 90 VAC. Is that correct?
Sorry. Lots of questions in one post.
Thanks in advance for any info, ideas, suggestions, etc.
Best Answer
For quite a while, Sparkfun had a series of wireless desk phones with the circuit housed in an old Bell System 500-style case. So you could have an old-style black desk phone with a rotary dial and old-fashioned ringer, powered by a Li-Poly battery and connected to the telephone network by a cellular modem.
Since there was no phone line to activate the ringer, they built their own high-voltage circuit. These phones have been retired from the Sparkfun catalog, but per their policy the information is still available including schematics and datasheet.
Here is a link to the schematic. The high-voltage ringing circuit is on page 3, which I have copied below: