Where is the high limit switch on a Trane XE90?

Any good telephone switch with Resistance Limit of 2000 up and attenuation 5db up?

• We have our project to design a telephone system and for long distances I'm looking for a good telephone switch with good attenuation and resistance limit, its hard to search in the internet as it displays only network switches, or any telephone switch with attenuation and resistance limit is acceptable, thanks for your help in advance, badly needed. :)

• Answer:

  I don't understand the question.. because you seem to have made assumptions and not given enough facts. and seem to be asking for a switch when you are meant to be designing one ? All (analog) telephone systems are based on 600 ohm balenced lines on -48v (nom) DC lines. If used with proper balenced/impedence matched cables (i.e. telephone cables) these go for many Km/Miles without amplification - as witnessed by the rural phone systems in place around the world. So what are you considering long distance ? 50 Km ? 100 Km which are really trunk lines.. or 10-20Km local lines ... Likewise, most systems are now going digital, thus removing the noise element from the quality of the link and allowing simpler amplification/restoration of signal than analog for trunk lines. There is then the VOIP/SIP IP based systems... which does all of the above. see Asterisk - Linux based IP exchange http://en.wikipedia.org/wiki/Asterisk http://www.asterisk.org/ AFAIK systems are therefore not defined in the terms you seem to be doing, A switch itself will have no attenuation but may add amplification (if analogue) The resistance part... I have no idea where you are intending this to be placed/located. So are you designing a switch or selecting one for use in a 'system' that you are building.. and how many lines for the local loop.