Vance Shipley <vances@xenitec.on.ca> (06/15/91)
Installing DID circuits was one of my favourite parts of PBX installs. Negotiating with the Bell installer as to what would be provided and how was highly amusing (and not a job for a craftsman who was not knowledgable and confident). It was often a trying affair to actually get the DTMF dialing arrangement I had ordered, the Bell technician insisting that dial pulse was "how it works". Many of the installers had had no experience with DID and were not certain exactly how they worked and consequently could not test them. I remember trying to convince one guy that I was to provide the battery on the loop and not the CO. He was only convinced after talking at length with his counterpart in the central office. But the hardest task was always getting the power fail circuits provisioned. With conventional trunking the trunks are usually switched to single line sets for emergency answering positions. With DID the battery for the loop is provided by the PBX so the circuits themselves will not work if the PBX goes down. In order to continue service calls must be routed over other conventional trunks to the customer premises. If this cannot be done then the calls should be routed to intercept in the CO to alert callers that service is temporarily unavailable. The CO would be signaled to switch to alternate routing by a seperate lead which was either normally grounded and opened under power fail condition or vice versa. These alternate routing arrangements were part of the DID service and did not require any extra charges but actually getting them in was a job in itself. This leads me to one of my stories of devious ingenuity. My boss had sold a PBX to a company and in his usual style had not confirmed that the switch could actually do what he had promised it would. The customer wanted DID to allow callers to reach people in their offices after hours. During the day the same numbers would reach the attendant. I just could not get the switch set up in this way. I let my boss sweat over this for a week and then told him how we could do it. We would trigger the power fail switch for the DID circuits whenever the attendant was manning the console! This caused the calls to the DID lines to be routed over the conventional trunks and terminate on the console. I was not for this plan but it did work and got him out of trouble. It scored me some points also :'>. I was always amazed though that Bell never noticed the frequency that these "power fails" occured (every weekday from 9 to 5). Vance Shipley vances@xenitec vances@ltg ..uunet!watmath!xenitec!vances