Published in the September 1983 issue of the SMPTE Journal, I hope Bill Carpenter, Ampex and the
SMPTE will not object to me including this historically interesting article for the sake of completenes.

(It is perhaps interesting to consider that while Ampex was seemingly well aware of the probable
impending digital revolution, analog being the 'moving target' described here, they appeared to be
oblivious of the de-facto arrival of Betacam...)

The Type-C Format - A moving Target

By William F. Carpenter

The SMPTE 1-in Type-C videotape recording format adopted five years ago has resulted in a family of
videotape recorders that have been widely accepted by both broadcasters and production studios. This
article reviews the changes in features and performance of the various Type-C format VTRs from the
first units available through the most recent developments in both studio and portable VTRs. This article
informs the VTR user of the state of the art of the Type-C format and partially explains the effects that
this 'moving target' has had on future developments.

When the SMPTE 1-in. Type-C format was agreed upon in 1978, there were doubts in the minds of
many as to whether it would ever replace the quadruplex VTRs that were in use worldwide. Most VTR
users could understand the projected economies of this new format, specifically in reduced tape cost and
the resulting reduced space required for archival storage of the tape. Also, the performance features of
picture in shuttle and still frame provided by the one field/scan format held a future of increased
productivity in the editing area. In addition to these basic improvements over quadruplex in both
performance and economy, there was intrinsic value to the mobile production user of reduced size,
weight, and power, all basic concerns in the growing field Production environmcnt.

This article traces the Type-C for- mat from its meager beginnings through the current generation of
products and identifies many of the important milestones along this path in both studio and portable
VTRs.

First Generation Type-C Products

In the beginning, once the SMPTE Type-C format had been agreed upon , two products aimed at the
educational and industrial marketplace emerged. These two machines, the Ampex VPR-2 and the Sony
BVH- 1000C, were the pioneering Products in this helical revolution.

The application of these machines in the broadcast/production market place soon brought requests from
users for additional features. Many of these feature changes were requested by production oriented users
as a result of the inroads these machines were making into the editing environment.

Simple two-machine editing employing the backspace techniques originally proven in the 3/4-in. formats
proved to be faster and more convenient than the previous quadruplex editing methods. The accuracy of
the tape timers, when updated by control track combined with the picture in shuttle and still frame
capabilities, made the production very similar to film editing. The speed of decision making was greatly
increased by eliminating the lengthy on-the-fy ''black-video-black'' or ''video-black-video'' type of
rehearsals that were commonplace with quadruplex VTRs.

In addition, a scan-tracking system employing a moving head brought a new dimension to sports
broadcasting. The capability of one machine in a mobile van to be used as an isolated recording device
and to be available lmmediately for instant slow motion replay has increased enjoyment for the sports
viewing Public worldwide.

These capabilities were of value for teleproduction users also, since now variable-speed effects could
be used in any video production without a video disk recorder. Some of the features requested during
this period included spot erase of the various audio tracks, reverse slow motion, and built-in time-code
generators and readers.

At this time, two additional manufacturers joined the ranks of Type-C format producers - Hitachi and
NEC. Their machines included the feature benefits of the previously mentioned VTRs and added some
innovations of their own, such as audio confidence and air guiding in the scanner area.

Development of Portable Type-C VTRs

Similar developments were taking place at the same time with portable place at the same time with
portable Introduction, the portable production requirements were handled by the Ampex VR-3000 in the
quadruplex format and by the various 3/4-in. machines heavily used in ENG applications. Separation
between these two formats was great, both in picture Performance and features. On one hand, there was
the accepted quadru- Plex picture quality, but combined with the complexity and weight of the Quad
format. On the 3/4-in. helical side, there was the simplicity of cassette !oading and lighter weight, but
the performance with the color-under system lacked the picture quality required by a large portion of the
teleproduction marketplace.

The three Type-C format portables, all of which appeared in the market place within a 9-rnonth period,
ranged in features from basic acquisition to fuII-featured field production units Including cue-controlled
editing and color video confidence replay. These machines were immediately pressed Into service by
the growing number of mobile teleproduction users of the Type-C format, but the weight of these units
still limited their true portability as compared to either 3/4-1n. or film Production.

The weight reduction in the change of formats from the previously used quadruplex VR-3000 was
between 5% and 15%, depending on the features of the Type-C format portable. This meager weight
reduction was related to Lhc (act that the record time had been increased from 20 min to 1 hour with the
associated increased battery capacity. These units though labeled ''portable'' by all manufacturers, were
carried in small vehicles or handcarts for field production use.

Introduction of Second Generation Products

At the I980 NAB show, the first of the second generation of Type C format VTRs was introduced -
RCA's TR-800. This product could truely be called second generation since it included a new transport
design that would handle 2-hour reels and had a microprocessor-based control system. It also featured
an increased scan-tracking range from -1 to + 3 times play speed and a sophisticated built-in time-code
editing system. Though this machine was the first Type-C format product produced, RCA had gained
considerable experience by marketing private labeled products since the start of the Type-C format
revolution.

At this time, feature additions were made in the majority of the first generation machines with B models
or evolutionary model number changes to Identify the later versions. One of the additiona features
required by an expanding portions of the marketplace was lncreased record/play time, and some
manufacturers modified their basic machines to include 3-hour tape capacity in unique console-sized
versions.

At the 1982 NAB show, two second generation Type-C format VTRs with some striking similarities
were added to the marketplace. One of these products, the Sony BVH-2000 included the increased 2-
hour tape capacity and microprocessor-based servo System and the increased scan-tracking range of the
TR-800. In addition, three control panels were available to allow this VTR to be applied over a
broader range of user requirements. It is interesting to note that all of these VTRs were aimed at the
overall broadcast / production marketplace, with very similar features and associated cost.

The other second generation VTR introduced at NAB l982 was the Ampex VPR-80. This product was
also similar to the previously mentioned second generation VTRs since it included the new transport
with 2-hour tape capacity and microprocessor based servo and control systems.

However, at this Point the similarity changed since, rather than being designed for the same marketplace
as all of the previous studio VTRs, this recorder was aimed at a different segment. Its goal was to
provide a no frills, cost-effective package for those teleproduction customers desiring to move up from
the 3/4 in. or a general-purpose machine for the day-to-day needs of the broadcaster. This machine
included extensive editing capabilities and built-in diagnostics similar to the other second generation
VTRs. But the variable speed mode was limited to a range from 0 to +1 1/2 times normal speed, which
had been proven adequate for typical Play-back-to-air sports applications but not for the high end of the
teleproduction marketplace.

To summarize the status of the Type-C VTRs from their introduction in early l978 through I982, in a
period of slightly more than four years, five manufacturers produced seven different studio VTRs plus
their three hour derivatives and three different portable VTRs. These products en- compassed two
generations with the second one consisting of evolutionary changes based on customer requests and
comments on the original products. This rapid development provided a ''moving target'' for other digital
developments.

Third Generation Products

Later in 1982, at the lnternational Broadcasting Convention (IBC), two third generation Type-C format
products were introduced which further increased the ''target range'' to be reviewed by any Potential
digital VTR manufacturer. The first of these products was the Ampex VPR-3 studio videotape recorder,
which can be classed as third generation since It included some revolutionary engineering concepts
previously unavailable in a Type-C format VTR. The first and most obvious revolutionary change was
in the area of tape handling. The VPR-3 includes a combination of air and roller guides to virtually
eliminate the friction buildup normally found in the tape path of a Type-C format videotape recorder.
These guides are used in all tape movement modes to provide fast, gentle, precise tape handling without
damage to the valuable master tape.

The next revolutionary change to the transport was the elimination of the pinch roller and the use of a
vacuum capstan which controls tape speed in all modes of operation. This concept, which has been
proven in thousands of broadcast VTR transports, allows the tape to be accelerated to its full shuttle
speed from play speed without transfer of the controlling elements. Since the tape is under capstan
control at all times, the addition of a high-resolution tachometer to the capstan assembly allows all
servo systems to sense precise tape speed and direction at all times.

The results of this revolutionary third generation tape transport can be seen in the typical acceleration
and cue profile graphs. The acceleration graph shows that, with the 1 hour tape reels normally used in
the teleproduction environment, the machine is up to the full 30 times play speed shuttle velocity in less
than 1 sec. The typical cue profile graph indicates that the machine can cut back to the start of a 30-sec
segment and roll in less than 2 sec.

In addition, the VPR-3, through the use of a field based color framing system senses on which field the
tape is parked at all times, and combined with the fast acceleration of the capstan system, is up to
operational speed in one field. This results in a fully synchronous operation in which the machine will
play back synchronously with the facility in a maximum of four fields on NTSC or eight fields in PAL.
That is, if the machine is parked on Field 1 on NTSC and PLAY is pressed, it waits until the next Field I
appears on the reference signal, starts the tape moving, and is up to speed by Field 2. The dynamic scan-
tracking system that is directed by the tachometer on the capstan allows disturbance-free pictures during
this interval. Other revolutionary developments in this machine include a front panel sync to subcarrier
phase meter, that allows faster tape editing without the possibility of picture shifts.

The audio system on this VTR uses the audio confidence head and distortion and level measurement
circuits to allow all of the audio record parameters to be automatically optimized on any videotape
stock. The video system is also automatically optimized. The control system of this third generation
VTR is microprocessor-based. A second microprocessor is used to control four additional VPR-3s from
the control panel via the proposed serial communications bus concept.

The other product that was introduced at IBC was the VPR-5, a lightweight portable field teleproduction
VTR. This product is classed as a third generation VTR because a totally new concept was used to
reduce both weight and power consumption. This VTR is a result of a joint engineering effort between
Kudelski of Nagra audio fame and Ampex.

The revolutionary feature of this machine is its 15-lb weight, complete with a 20-min reel and battery.
This results in a one-person field production operation when used with a lightweight camera. This was a
major reduction from the previous portable Type-C format machines which all fell in the 45- to 55-lb
range. The weight reduction in this product was accomplished by attention to the power consumption in
all circuitry, so that battery size and weight could be reduced without affecting performance. The second
major emphasis was to reduce the weight of all component parts.

There are no castings used in this VTR, but the majority of metal parts are machined from solid Type
7075 aircraft aluminum alloy which has a tensile strength rivaling that of steel. These parts are machined
with precise strength-to-weight dimensions, eliminating every gram of material not required in the VTR.
The major components on the top plate, scanner, and reel motors are designed so that they do not
protrude below the top Plate, which allows the maximum space for the electronics package.

The majority of the electronics are contained in small PWAs that contain the small-outline components
packages. Since these are leadless components, automated manufacturing techniques and vapor phase
soldering were used and resulted in extremely lightweight and highly reliable circuit modules. This
product, as were the other second and third generation VTRs, is microprocessor based; the
microprocessor is part of the intelligent power control system and shuts off various components when
they are not needed. This increases battery life. The VPR-5 also includes cue-based insert and assemble
editing control. The unit also can be used with 1-hour reels in an unenclosed bench-type operation.

Conclusion

Since its adoption in I978, use of the Type-C format has expanded greatly. It is now used in 12 VTRs of
3 different generations. It provides an even larger target for digital formats of the future.

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