| ??? 10/16/07 10:55 Read: times |
#145802 - Beware! Responding to: ???'s previous message |
The precise specification depends on your network supplier.
For BT, these are published at http://www.sinet.bt.com The common nominal voltage is -48V, but the ringing voltage can be much higher - 75V AC or so - so beware! Also Beware that there may well be legal and/or regulatory issues with connecting equipment to the public telephone network See, for example, http://www.8052.com/forum/read.phtml?id=132540 |
| 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 |