and if you were able to buy one somewhere, you could not connect it to the telephone system. They were very strict about this. As well, you could not add an extension phone. Supposedly the phone company could detect a violation of their policy by checking the "ring current". If your line drew too much current, you had an illegal phone attached and had to pay an extra fee or remove the phone. They owned the phone and you leased it. If you wanted a different type or your phone ceased to work, a phone repair person had to do this. Wall phones were hard wired but desk type (all black) could use a large 4 prong jack. Modulars came later. There was a time when our local phone company offered us a choice of either buying our current phone or continuing to lease it. If you bought the phone and it broke, you had to buy another. If you continued the lease, you had some repair coverage. It was later that phone stores emerged and other manufacturers got into the business of making phones. These still had to meet certain specifications...ring current being a big issue. Today, my phone company is only responsible for hardware up to the outside interface. The rest is mine unless I contract them for inside wiring service. I'm quite capable at doing my own wiring so it's no issue. Still, when I have trouble on the line, the phone company threatens with huge charges if they determine their end is good. Checking for problems is as simple as connecting an extension phone to the outside interface. If the problem can be reproduced there, it's their problem.