4 ms·

> same power source as the doorbell coils Beautiful thinking. I wonder what other obscure sources for voltage in a house could be used? The HVAC head unit, ana

by adolph 3y ago

> same power source as the doorbell coils Beautiful thinking. I wonder what other obscure sources for voltage in a house could be used? The HVAC head unit, analog telephone, ... The POTS [(Plain Old Telephone Service)] phone line, with all phones on-hook, should measure around 48 volts DC. This drops down to the 3 to 9 volt range when a telephone on the line goes off-hook. An off-hook telephone typically draws about 20 milliamps of DC current to operate, at a DC resistance around 180 ohms. The remaining voltage drop occurs over the copper wire path and over the telephone company circuits where there is usually 200 to 400 ohms of series resistance to protect from short circuits and decouple the audiocircuits. https://www.jkaudio.com/article_03.htm https://www.jkaudio.com/article_03.htm

westurner 3y ago
If the POTS cables daisy-chained between the telephone jacks after the telco's box are 4-pair Ethernet, there are 8 wires between each receptacle/port less 2 wires for each phone line. If only one phone line has ever been connected and there are 4pair (Ethernet,) cables between the phone jacks, there are 3 spare wire pairs that could be connected in a local private closed loop in order to carry (modulated) DC voltage for other applications; though you'd need to put like a thermal sticker label after the box and behind/on all the phone jacks to warn about the voltage (which is a presumed risk when handling 4pair cabling as an installer, as a (demo) contractor, as a future occupant) Gigabit Ethernet uses all 4 pairs for data, so Gigabit PoE and faster must have data+power on one or more pairs. From https://en.m.wikipedia.org/wiki/Power_over_Ethernet https://en.m.wikipedia.org/wiki/Power_over_Ethernet : > In addition to standardizing existing practice for spare-pair (Alternative B), common-mode data pair power (Alternative A) and 4-pair transmission (4PPoE), the IEEE PoE standards provide for signaling between the power sourcing equipment (PSE) and powered device (PD). This signaling allows the presence of a conformant device to be detected by the power source, and allows the device and source to negotiate the amount of power required or available while avoiding damage to non-compatible devices.

by adolph 3y ago

westurner 3y ago

If the POTS cables daisy-chained between the telephone jacks after the telco's box are 4-pair Ethernet, there are 8 wires between each receptacle/port less 2 wires for each phone line. If only one phone line has ever been connected and there are 4pair (Ethernet,) cables between the phone jacks, there are 3 spare wire pairs that could be connected in a local private closed loop in order to carry (modulated) DC voltage for other applications; though you'd need to put like a thermal sticker label after the box and behind/on all the phone jacks to warn about the voltage (which is a presumed risk when handling 4pair cabling as an installer, as a (demo) contractor, as a future occupant) Gigabit Ethernet uses all 4 pairs for data, so Gigabit PoE and faster must have data+power on one or more pairs. From https://en.m.wikipedia.org/wiki/Power_over_Ethernet https://en.m.wikipedia.org/wiki/Power_over_Ethernet : > In addition to standardizing existing practice for spare-pair (Alternative B), common-mode data pair power (Alternative A) and 4-pair transmission (4PPoE), the IEEE PoE standards provide for signaling between the power sourcing equipment (PSE) and powered device (PD). This signaling allows the presence of a conformant device to be detected by the power source, and allows the device and source to negotiate the amount of power required or available while avoiding damage to non-compatible devices.