Analog Lines In The 21st Century?

Getting old is a pain in the neck! Literally and figuratively! I am trying to figure out the benefits of getting older and I am not coming up with a very long list. You built a library of experience; I guess that must count for something. There is new generation of telecom professionals that have no idea what a cross bar switch is, but so what. Nobody is really missing buggy wipes either. In the old “Bell System” (I have really dated myself now, as Google demographics tell me my readers were born post breakup) there was a specific regulation against the interconnection of analog telephone lines on an PBX. Now part of that restriction was the Bell System being a bunch of anti-competitive jerks, but there were also real technical issues for not doing so. Analog lines are most useful in man-to-man communication. The issue here is the concept of “answer supervision” and “calling or callED party disconnect”.

When you answer the ringing phone in your house, the answer supervision is actually your ear. You can “hear” the other party. Yes, there is a line reversal or voltage change but being a two-wire loop is nothing like being a trunk line. For that reason we use trunks to interconnect machines to machines. Every go to make an outside phone call, and find someone on the line? Great example of “glare” the concept of a call ringing in just as you where grabbing it to make an outside call. Analog lines are good for key systems with winking and blinking line keys that show everyone who is on what line, but they are a real annoyance on a PBX system.

Answer supervision is poor if it exists at all and glare can be a real issue. Throw a couple of Centrex lines in the mix and you will get some real extra fun features. Nothing like having analog lines connected to your PBX that have feature treatments you did not know about. It is always phone when the phone companies VM picks up before your ShoreTel VM system does! As a rule you might like to have one analog line at a site for 911 and power failure, but the idea of running a ShoreTel PBX with a rack full of analog lines, actually makes me ill. Judas Grunt, it is the 21st century already! Can you spell SIP?
ShoreTel does a reasonably good job with analog lines given the real disadvantage they have in the area of answer supervision, etc. ShoreTel actually goes off hook on these lines at timed intervals. If it does not “hear” dial tone, it marks the line out of service. If you are really cleaver, there is a trick to recording the sound made when the line goes “off-hook” so you can retrieve the wav file and play it back locally. A great lifesaver when you are in Portland and your trouble shooting a local loop in a remote site, just outside Minute, ND and nobody is in the office.

It amazes me that we still have analog lines on PBX systems, but as long as we do, we might as well learn how to deal with them

By: Peter Buswell

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