| ??? 09/21/09 17:05 Read: times |
#169024 - In old systems ... some of which are still in use ... Responding to: ???'s previous message |
Its on the order of 130 volts to either side of the negative 48-volt battery on U.S. phone systems, and, IIRC, that's the minimum. Since it was originally a current-loop (back in the circuit-switched days) and since there are still a few places where that's still in use, telephones have to tolerate it. In the current-loop systems, that voltage can go as above 300 volts p-p, again, on centered about the standard negative 48-volt battery, which is the on-hook voltage between tip and ring.
I haven't worked with this stuff in many years, but it seems to stick with me ... maybe it's because of those 300 VAC ... RE |
| Topic | Author | Date |
| Detecting AC voltage..... | 01/01/70 00:00 | |
| Thoughts... | 01/01/70 00:00 | |
| ring-detector? | 01/01/70 00:00 | |
| The voltage range appears to be in the same ball-park | 01/01/70 00:00 | |
| In old systems ... some of which are still in use ... | 01/01/70 00:00 | |
| Don't use a relay | 01/01/70 00:00 | |
| I was thinking optocoupled triac driver ... | 01/01/70 00:00 | |
| Capacitor or Relay | 01/01/70 00:00 | |
| Capacitive dropper | 01/01/70 00:00 | |
| I used it for a long time in traffic lights controllers | 01/01/70 00:00 | |
| Capacitive Dropper | 01/01/70 00:00 | |
| Ideas Appreciated | 01/01/70 00:00 | |
| Strobed measurement to minimize heat dissipation | 01/01/70 00:00 | |
Clever Concept | 01/01/70 00:00 |