It is not rocket science to build a device that properly meets telephone communication specifications and also is built well enough to ensure no power or other improper currents or signals get into the phone line, and the device does not unnecessarily go off-hook or otherwise misue the network. From the descriptions various posters have made about the devices, an awful lot seemed to be done really cheap, quick, and dirty.
I respectfully wish to offer some comments about monopolies, excluding competitors, and a level playing field.
First, as to public policy and monopolies:
Yes, the Bell System and Independents were assigned a deliberate monopoly which deliberately excluded competitors. But in return for that privilege, they had many restrictions on their business. They certainly could not charge rates to maximize profit, but rather had to charge low rates to maximize a customer base. It certainly would've been far more profitable for Bell to charge a higher minimum monthly rate and not have to be bothered providing unprofitable full service to very marginal subscribers.
Further, the Bell System was severely restricted from going into other lines of business. The Bell System with Western Electric and Bell Labs could've been a powerful player in industrial electronics and computers. Bell was mandated to license all Bell Labs discoveries at modest cost, not reap the profits from it. (Today, pharmaceutical companies make big profits from their research.)
Bell never made the kind of profits that a typical technology company of its times would make. American industry was in a long boom between
1950 and 1970, but the Bell System , despite its power technologies, was not part of it by deliberate design.So, yes, Bell was almost guaranteed to make a profit, but--at the same time--it was likewise guaranteed never to make huge profits.
Let's look at it another way: Suppose you own a restaurant and the government requires you to meet very stringent--and costly--food safety and public service standards. You are mandated to feed the homeless and be open with a full menu 24/7 , for example. Then the government, to provide a so-called "level playing field", excuses newcomer restaurants from meeting those same safety and public service standards; they don't have to be as clean, feed the homeless, or be open 24/7. Is that truly a "level playing field"? Is that truly in the public interest?
We must remember that after MCI gained a foothold Bell sought revised _lower_ rates to meet competition; rates that were based on competitive cost, not widespread averaging. Bell's applicaton was denied. Is that a level playing field?
Secondly, as to technology:
If your neighbor buys a modem or builds his own that fails to have proper safety precautions or uses crappy or wrongly installed parts, your neighbor could introduce power or interference current over a phone line and disrupt your service or even create a safety hazard, despite the system safeguards. Such "competitors" should be excluded. In reality a lot of crap was sent over Bell lines and it bore the cost of the cleanup. (A disrupted customer would call 611 and Bell would send a man and truck out to check it out but find nothing, because the offending customer would quickly disconnect the errant device.)
Let's look at another example:
In the 1960s, IBM revised its policies and allowed third party vendors to build peripherals (tape and disk drives) for connection to IBM's System/360-370 mainframe computers. A big business sprang up and vendors were able to undercut IBM's prices. Helping the vendors was IBM's Consent Decree, similar to Bell's, where it was required to license out its research results for a nominal fee. Also helping were former IBMers using their experience at a new company.
But when IBM, thanks to its research, wanted to upgrade (change the standards) its peripherals or lower prices--a better deal for customers--the changes would instantly obsolete the 3rd party vendors' offerings and financially hurt them. The 3rd party vendors cried foul, calling it unfair competition. I believe the court found IBM's actions to be exactly what competition was supposed to do: IBM's improvements benefited its customers and it was up to the competitors to go along.