> The reason for not detecting dialtone is cost. The equipment involve is > intended to be cheap. As we know all to well if there is any way to cut > costs some companies will go to any length. I personally don't like blind > dialing. The time delay before dialing is required to be 10 seconds > minimum. I used to cheat and use 7 seconds. We never had any complaints of > mis-dialing because CO wasn't ready by the time dialing started.
Duane, I remember that cost was an issue before we had chips. I also seem to remember that with the advent of chips, that became a non-issue where I was working (Nortel Apparatus Division). Admittedly, we did not make five-dollar automatic diallers. > > I re-read Bell Technical Reference Pub 47001. I stand corrected on ground > start, it does use dialtone. > > I now remember the equipment design I did for a ground start network. It > was in the late 1960's for a mine in South America. They had a ground > start system in a very extensive mining operation. It was an alert system > used to detect methane and carbon dioxide levels in a mine. The detection > circuits flagged an emergency ventilation system and turn on alarms very > quickly. This Ground start system didn't have dialtone. It just looked > for the presence of loop current, waited 200 mS, then began alerting the > ventilation and alarm system via DTMF. All quipment was inside gas tight > housings to eliminate the possibility of an explosion when relays arced > during opening and closing. I worked for 15 years in Northern Quebec and Labrador for a mining and railroad organization. We had all manner of weird all-relay PBXs, Strawger switch PBXs and Philips Rotary PBXs, many of them ground start. The de-watering alarms in the pits were also connected via the PBX to my home. We did some wonderful work keeping all this stuff talking to each other. Some of them would accept dial pulses before dialtone was extended, but I didn't think that type of equipment was used anywhere in the world any longer. (How many competent Strowger switch adjusters do you still know ?) Ciao, Vic
