Photon Pacesetter phototypesetter controller and core

Rough draft, last updated Dec 24 2017. Edited by Herb Johnson, (c) Herb Johnson, except for content written by others. Contact Herb at, an email address is on that page..


I acquired in the fall of 2017, a Verisystems P16 core memory board with two controllers, and the TTL-based programmable controller "logic" built in 1972. No docs, no other hardware. So I"m working out how the core and controller work and connect, as I research the original Verisystem product from the early 1970's. Why? This is what "microcomputing" looked like before microprocessors. I show more vintage computing from my restorations home page.- Herb

Verisystems P16 and Photon Phototypesetters

Links to the background of Graphicomposition, Photon and 1970's photo-typesetting. There's press releases in Computerworld magazine (a trade journal) in 1972 for the Varicomp 1000, "a VariSystems PAC-16 programmable computer, an 8K-byte processor with word length of 16 bits. Additional 8K Byte memory is optional Read/write cycle time is 1 msec, instruction fetch time is 6 msec, and instructional execute time is 3 msec. Pricing for the basic Varicomp 1000 System is $7950..." (June 21 1972, page 17)

from DigiBarn

see Barry Yarkon's descriptions at DigiBarn

Graphicomposition's main typesetting device was the Photon Pacesetter MkI phototypesetter, an analog-digital step-and-repeat device whose stepping motors and solenoids and xenon flash tubes were controlled by a 16-bit digital controller, the Varisystems P-16 (Plainview, NY). It used a socketed array of TTL logic ICs on a hinged wire-wrapped motherboard above a cabinet filled with connectors, cables, pots and power supplies. AC to DC conversion and signal shaping were rudimentary. Typefaces were negative character shapes arranged serially around the circumference of glass master discs that spun around at high speed as each character was exposed by a brief flash of light, and displaced along the line of type being set by a moving right-angled first-surface mirror system. By today's standards this sounds Rube Goldberg-like, but it was near state-of-the-art in 1975.


From this description by Clark E. Coffee of Photon Pacesetter:

By the late 1970s, Photon was seeing its markets erode. According to the book, Words Into Type, (Prentice Hall 1974) "by 1972 over 100 machines to set type photographically were on the market". Photon responded by launching a crash program to develop a low cost machine to be called the Pacesetter and by marketing the Photon 7000, a CRT machine developed for Photon by another firm.

The Pacesetter was a very fine electro-mechanical machine, potentially a major threat to the Mergenthaler and Singer machines. But its crash program was a very expensive way to develop anything. The machines were late coming out. In desperation, some were shipped as late as the end of January 1974 with December packing slips so the sales could be credited to the last quarter of 1973. One technician described them as "going out with wires hanging out of them." The local sales and servicing offices were promptly swamped with problems that should have been solved at the factory. There weren't any spare parts, so they'd cannibalize the first machines rejected by angry buyers, to try to keep, or get, the others running. Within the year Photon had closed its doors. But some of the Pacesetters had long, useful lives.

From the US Patent Office

Free Patents Online snagged a copy of US Patent 3833887, as did Google.

Programmable controller, US 3833887 A, Abstract: "A programmable controller for use in controlling a wide variety of external data and production devices and having an extremely flexible stored program capability enabling the device to function as a small-scale computer adapted for use as either a systems controller or as a "stand alone" minicomputer."

Publication date Sep 3, 1974; Filing date Oct 30, 1972. Inventors: R. Shevlin. Original Assignee: Varisystems Corp. There's an interesting list of examiner reference-by's. Toyoda in 1974, Xerox in 1977, Sharp in 1988, LSI Logic, Sun Microsystems, even Fanuc LTD.

Computer History Museum has Title: "Introductory manual for PAC-16 programmable adaptable controller" Catalog Number 102679132, Date 1971 ca., Publisher, Varisystems Corporation. Lot Number X2592.2004. Also, Title "PAC-16 programmable adaptable controller", Catalog Number 102679133

Example of Verisystem Photon phototypesetter

[Photo typesetter]

Photos below courtesy of Jack Rubin, who came across this Photon model in Dec 2017. - Herb

- Photon Pacesetter 84front-panel and controller are below
- front panel and TTL controller
- controller front-panel
- left-hand control panel
- right hand control panel
- front label

Core and TTL programmable controller

Verisystems P16 controller logic and core memory for a Photon Pacesetter phototypesetter. I got this board-set in October 2017, courtesy of Jonathan Chapman. At the least, I decided I could likely decode the core controller interface. Possibly, with more product information, I could display the boards and a mock control-panel for the controller. Some research found documents which confirmed this was a chip-level implementation of a programmable controller. This was how such controllers were developed in the early 1970's, just before microprocessors. The "logic" itself dates from 1972.

[Photo typesetter]

- core board atop core controller board
- core controller w/o core on top
- core controller interface connector
- core controller interface, shows PC traces.
- core controller some interface ICs

[Photo typesetter]

- TTL logic, top view
- TTL logic, bottom view
- logic, label with 1972 dates

Dec 2017 control/data pinout of Varisystem core board

Summary: looks like 12 address lines, 4096 locations or 4K RAM
two sets of 8 lines, probably read or write data
four additional function lines, probably control and status

Connectors are PJ9/MJ2 and PJ8/MJ1, 2 X 13 pin connectors. Here's how I'll establish pinouts.

2  4  6  8 .....20 22 24 26
1  2  3  4      19 21 23 25

PJ9	to
1	gnd
2	gnd
3  #1 7495 pin 2	input 1A
4  #1 7495 pin 3	input 1B
5  #1 7495 pin 4	input 1C
6  #1 7495 pin 5	input 1D
7  #2 7495 pin 2	input 2A
8  #2 7495 pin 3	input 2B
9  #2 7495 pin 4	input 2C
10 #3 7495 pin 3	input 3B
11 #2 7495 pin 5	input 2D
12 #3 7495 pin 4	input 3C
13 #3 7495 pin 2	input 3A
14 #3 7495 pin 5	input 3D
15	gnd
16	gnd
17	gnd
18	gnd
19 #8 7401 pin 1	output
20 #4 7401 pin 1	output
21 #7 7401 pin 1	output
22 #3 7401 pin 1	output
23 #6 7401 pin 1	output
24 #2 7401 pin 1	output
25 #5 7401 pin 1	output
26 #1 7401 pin 1	output 

1	gnd
2	gnd
3  #8 7401 pin 5 	input
4  #4 7401 pin 5 	input
5  #7 7401 pin 5 	input 
6  #3 7401 pin 5 	input 
7  #6 7401 pin 5 	input 
8  #2 7401 pin 5 	input 
9  #5 7401 pin 5 	input 
10 #1 7401 pin 5 	input
11	gnd
12	gnd
13	gnd
14	gnd
15 7402 pin 2	input
16	no conn
17 7402 pin 5	input
18 7400 pin 1	input
19	no conn
20 thru diode and R to 7404 pin 4 output and transistor
21	gnd
22	gnd
23	gnd
24	gnd
25	gnd 
26	gnd

TTL Chips for I/O

7495 - 4 bit counter, pins 2, 3, 4, 5 are inputs A B C D to counter.
7401 - quad 2-input NAND gate, pin 1 is output of 2/3,
       pin 4/5 inputs to output 4.
7402 - quad 2-input NOR, 2 input, 5 input
7400 - quad 2 input NAND, 1/2 input 3 output
7404 - hex inverter, pin 3 in to pin 4 out

 7495   7495   7495         chip placement
  #1     #2     #2      left to right on board

 7401 #1                   chip placement
 7401 #2
 7401 #8                top to bottom on board

this is my chip-location numbering, manuf. numbering unknown

Contact information:
Herb Johnson
New Jersey, USA

This page and edited content is copyright Herb Johnson (c) 2017. Copyright of other contents beyond brief quotes, is held by authors of that content. Contact Herb at, an email address is available on that page..