| ??? 10/18/07 07:01 Read: times |
#145877 - Your circuit diagram shows it adequately Responding to: ???'s previous message |
The earth side, whether that's tip or ring, is typically clamped to near earth as shown, but also similarly in the application circuit, albeit at a lower voltage, often typically 80 volts, which is a nominal value for the peak above nominal GND on the positive side of the loop.
I don't remember whether it's tip or ring that gets the nominally earth side during the on-hook state, but, viewed from the standpoint of battery being at -48 volts, the ring signal is as I previously described it, and is easily detected by rectifying the signal relative to GND, and subsequently attenuating it as needed. I'm not expert in these matters, though I have built circuitry that met standards and did no harm. RE |
| Topic | Author | Date |
| Telephone line voltages | 01/01/70 00:00 | |
| Beware! | 01/01/70 00:00 | |
| about that -48 volts ... | 01/01/70 00:00 | |
| i did, OUCH | 01/01/70 00:00 | |
| the key is to remember it\'s a current-loop | 01/01/70 00:00 | |
| The old stuff | 01/01/70 00:00 | |
| OK... YOUR grandparents ... MY parents ... | 01/01/70 00:00 | |
| Great Stuff ! | 01/01/70 00:00 | |
| Pulse dialing | 01/01/70 00:00 | |
| Not really surprising. | 01/01/70 00:00 | |
| Not necessarily | 01/01/70 00:00 | |
| Here, it detects both | 01/01/70 00:00 | |
| Pulse Dialling | 01/01/70 00:00 | |
| Current Loop | 01/01/70 00:00 | |
| Why is that the key?? | 01/01/70 00:00 | |
| It's the key to understanding it | 01/01/70 00:00 | |
| Sorry, but I cannot see the evidence | 01/01/70 00:00 | |
| Your circuit diagram shows it adequately | 01/01/70 00:00 | |
| What do you intend to build? | 01/01/70 00:00 | |
What I want to build | 01/01/70 00:00 |