• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Ring Detection & Count

Not open for further replies.


New Member
Yes, if you put it in a plastic box, and NOTHING ELSE connects to it, just like a regular phone found on the market.

This is the same protection that is found in "double insulated" power tools.

What i was talking about in my previous thread was those projects (I've seen a lot of them, i even built one !) that interconnect between a phone line and, say, a tuner, tape recorder or audio amplifier. THERE, you need isolation.

And yes, you can be shocked by a phone line. When a correspondant calls and your phone rings, 90 Volts AC @ 20 Hz are sent to your phone line. If you touch the line with moist hands YOU WILL FEEL IT !

EVERY commercially telephone device that connects to something else (modem, phone line fed battery charger, telephone answering machine, cordless phone, etc...) that i've seen DO have isolation devices (Xfmr, relay, optoisolator) in them. From that fact, it's easy to conclude that isolation is REQUIRED in any devices that do not provide TOTAL isolation by their casing.


Depending on the country isolation transformers are legally required to meet telecom standards.
Not open for further replies.

Latest threads

EE World Online Articles