Broadband

[Lurch]

Excellent, someone else as pedantic as me. Now start on RJ11 and RJ12 confusion.

 

[jdmjrmdam]

A plug for a true RJ45 configuration will not fit the jacks used for Ethernet, as it has an additional keyway. RJ45 is a configuration for the connection of an analog modem, with adjustable output power controlled by a resistance in the jack and set to match the line characteristics. It's rarely ever found today.

It's fair to say that outside the telecomms industry the 8P8C modular plug used in voice and data cabling has come to be commonly known as RJ45 although as you rightly say it is not.

 

[ianmacd]

How is the power getting out there?

Wireless is great with externals as Steps has suggested. Had an 5db antenna on my roof about 10 years back and could pick up a signal with matching antenna about a mile away on the other side of a valley. Very cool. Bet with all the noise that won't work these days since everyone and their dog pollutes the waveband now. Directional's are even better.

RJ45 is a very widely used name but, as PBC points out, is not an RJ45. RJ45's had 2 connectors (with 8 positions, 8P2C) and the ones used for 10*BaseT is an 8 position & 8 Connection (8P8C) connector.

 

[PBC_1966]

We're certainly fighting a losing battle over the RJ designations when even quite major manufacturers are now misusing the terms. :|

A lot of people don't realize that the RJ numbers don't refer to the type of plug, but to both the type of plug and the configuration in which it's used.

RJ45's had 2 connectors

No, 4. One pair for the line, plus one pair for the connection to the resistance in the jack to set the modem's output power.

 

[jdmjrmdam]

We're certainly fighting a losing battle over the RJ designations when even quite major manufacturers are now misusing the terms.

Yeah, It's a bit like the way UTP cable is refered to as ethernet cable.

 

[ianmacd]

No, 4. One pair for the line, plus one pair for the connection to the resistance in the jack to set the modem's output power.

The resistor is housed inside the connector so it never left the jack hence its a 8P2C as only 2 connectors were usable.

 

[ianmacd]

Yeah, It's a bit like the way UTP cable is refered to as ethernet cable.

As opposed to STP?

 

[Lurch]

As opposed to STP?

Or FTP? "It's summink to do wiv computers innit"

 

[ianmacd]

LOL FTP is. But which one as I can think of at least 2?

 

[steptoe]

A plug for a true RJ45 configuration will not fit the jacks used for Ethernet, as it has an additional keyway. RJ45 is a configuration for the connection of an analog modem, with adjustable output power controlled by a resistance in the jack and set to match the line characteristics. It's rarely ever found today.

miseducation for me then

sometimes its good to be thick around computers....

 

[PBC_1966]

miseducation for me then

It's a common misconception for anyone not from a telecoms background who has seen the widespread modern misapplication of the designation, so don't worry, you're not alone. (Just remember to set others straight now you know! ).

It's quite curious as to how the misuse even got started, considering that the connectors aren't even the same, just somewhat similar in overall appearance if you ignore the extra keyway.

The resistor is housed inside the connector so it never left the jack hence its a 8P2C as only 2 connectors were usable.

The resistor has to be connected to the modem which is done via pins 7 & 8. The telephone line is on 4 & 5. For a line running from a 1A2 or similar key system, there would be another pair of connections for the KSU's A & A1 leads on 3 & 6.

 

[ianmacd]

The resistor has to be connected to the modem which is done via pins 7 & 8. The telephone line is on 4 & 5. For a line running from a 1A2 or similar key system, there would be another pair of connections for the KSU's A & A1 leads on 3 & 6.

Clearly my memory of them is somewhat different to yours then.

 

[PBC_1966]

The whole purpose of the resistor was to set the gain of the modem to match the line characteristics, increasing it on a line with higher losses and decreasing it for a line with lower losses.

The value of the resistor fitted in the jack (across 7 & 8) was chosen to match whatever the line characteristics happened to be for that telephone line as it appeared at that jack. When connected, the modem would "see" whatever value of resistance had been installed at that jack and adjust its gain accordingly to match the line.

Hang on, there must be a diagram online somewhere........

Here you go, last on the page:

http://www.phonegeeks.com/rjexanddiag.html