In 1940, a revolution occurred in the land mobile radio industry, namely that the successful installation of a large scale VHF FM two-way (actually called three-way, because of the two-channel transmitters) radio system by Fred M. Link and Daniel Noble for the Connecticut State Police proved its superiority over the older low frequency one-way AM broadcasts and AM in general. From that point on, all major manufacturers switched emphasis to VHF FM products and generally introduced no new-design AM equipment from that point onward. GE was no exception. This is not to say that AM equipment was not still being sold, just that purchasers were still buying models and designs dating from 1940, more or less. AM production by all major manufacturers stopped by 1950, other than by special order.

GE had already been building FM mobile equipment since 1938, well prior to Link and Noble's experiments, on a somewhat experimental basis, in coordination with Major Edwin Armstrong. Armstrong is usually referred to as the "inventor" of FM although at least one patent was taken out prior to 1910 describing FM transmission. Armstrong's patents, perhaps more correctly described, covered the first actual practical application of FM. GE had applied to the FCC for an experimental license for FM operation on 49 MHz which was granted on August 3, 1938.

GE ran comparison tests of AM vs. FM (at 15 kHz +/- deviation) on September 28-29, 1939, with Maj. Edwin Armstrong in attendance, for the FCC Emergency Service administration. One of the persons in attendance was Professor Daniel E. Noble of Connecticut State College.

A GE VHF FM two-way system was already in use by late spring, 1940, for the Douglas County, Nebraska Sheriff, consisting of a 250 Watt base station and a number of 25 Watt mobiles. Link's "first" FM system would have been being installed at relatively the same time, and despite attempts to whitewash it, was essentially a copy of the GE design. The Link Connecticut State Police system was the first large system to make use of FM, but the claim that it was the first VHF FM system is open to interpretation. Link's first FM equipment consisted of a modified 8UA VHF AM receiver and 15UBX AM transmitter from 1938.

GE was one of the few manufacturers to respect the Armstrong's patents on FM, and took out licenses to use that system, as did Link. Motorola did not, and was involved in litigation with Armstrong and Armstrong's widow (who eventually prevailed) well into the 1960's.

The initial GE-made mass production model FM mobile employed GE's E-1-A and E-1-B, which were large separate transmitter and receiver units, similar in physical design to Link equipment. One reason the units remained separate, other than weight and size constraints, is that purchasers often wanted to add only a transmitter to an already existing medium wave AM receiver installation in an automobile (California Highway Patrol, for example.)

It should also be noted that within months of completion of the Link system for Connecticut, Noble had joined Motorola, Inc. and Motorola was producing a two piece VHF FM radio of their own called the "Deluxe" line, which not surprisingly, appeared very similar to the Link 1940 FM equipment.

By 1941, GE had already revised and superseded their initial FM equipment of 1938 at least four times, making it somewhat more compact and updating some of the circuitry. These changes were referred to as " M.O.," for "manufacturing order." It should be noted that the first through third M.O. of GE FM equipment were actually manufactured by the James Millen Co. of Malden. Mass. using designs created by GE engineers in Schenectady, N.Y..

It is somewhat unclear what the "Fourth M.O." equipment designation was, other than that it was the first equipment actually manufactured by GE, at their Bridgeport facility, beginning in 1941. That equipment is believed to be the E-1 Series shown below. It is unknown what the Millen-made equipment looked like or the model designations, but it was a small quantity order.

Following the E-1 Series, the next generation of equipment would have typical model numbers of 4RMD and 4TMD, referring to the receiver and transmitter respectively. This was the second generation of VHF FM radios produced by GE itself, and many were sold. They are recognized by the tall, rounded cabinet tops with a single handle in the middle. The transmitter was dynamotor powered and used an 807 tube in the power amplifier. The equipment was available only in the 30-40 MHz range. At this point the "M.O." designations become murky. The 4RMD and 4TMD sets may be the "5th M.O." equipment, but in any case there were "4th" through "7th" M.O. equipment produced up to 1949.

In 1942, production of "emergency equipment" (police radio) was moved from Bridgeport to the Schenectady works to accommodate war production, and GE's efforts were primarily directed to that area, and then to Syracuse by 1945.

In approximately 1949, GE began production of a third and last generation of two-piece separate unit equipment, which saw large production figures and is the most recognized. This frosted-green colored equipment is usually referred to colloquially as the "Pre-Progress Line," because in 1955, GE introduced a highly successful series of radios called the Progress Line. The two-way radio industry then began calling the equipment which immediately preceded the "Progress Line" the "Pre-Progress Line," and even GE began to refer to it as such by the early 1960's.

GE insiders referred to the low band two-piece Pre-Progress radios as "8th MO," so apparently by the time these were designed, seven previous Manufacturing Orders had been completed of various styles and versions, as mentioned above.

In late 1954, GE began production of the enormously successful "Progress Line," a one-piece mobile radio made of interconnected chassis in a "basket" mounted inside a sturdy steel housing. The Progress Line would be made for ten years and was GE's flagship product. By 1959, the rush for solid state mobile radios caused GE to develop, perhaps prematurely, a radio called the "Transistorized Progress Line" or "TPL." These were generally regarded as a design failure with extremely poor reliability, and saw only a few years of production.

The Progress Line was made in a wide variation of models and combinations, and included portables (eventually), base stations, monitor receivers, railroad and so forth. Interestingly, there was no "Solocycle" (two wheel motorcycle) Progress equipment made, although a "Servicar" (three wheel motorcycle) combination was offered.

In late 1964, GE began production of the highly successful MASTR Progress Line, ceasing production of all previous models, and began a complete overhaul of the entire product line. GE from the late 1950's and onward also produced a secondary line of less featured "low cost" radios, including a dash mount VHF high band radio called the "Pacer" and a convertible-mount UHF radio called the "Accent 450." Both of which were essentially failures and reviled in the industry.

It is perhaps unfortunate that prior to the Progress Line, GE did not name the various equipment models. This makes it harder to refer to them in any convenient way.