Handmade 1982 Photo Telephone Device
In the digital age, our website carries on the legacy of electronics magazines, which once showcased projects to build, including picture phones. These devices, however, were not the modern video chat devices of today.
In 1982, Radio Electronics magazine published plans for constructing a picture phone. Initially, it may seem reminiscent of contemporary DIY projects with a Pi-Cam, but in 1982, the level of work required was significant. The device utilized a closed-circuit TV camera, a TV, a telephone, and a shoebox-full of parts.
While the term "picture phone" could be considered a stretch, as it used ham radio-style slow scan TV (SSTV) to send a frame of video approximately once every eight seconds, the technology was impressive for the time, offering a 128 x 256 image with a frame rate of 0.125 Hz.
Hams had long been experimenting with SSTV, using high-persistence CRTs to display images until the phosphor stopped glowing, and requiring the sender to remain still throughout the eight-second transmission period. However, modern circuits soon allowed for capturing the slow input and converting it to a regular TV signal for as long as desired.
Although SSTV never truly took off within telephone networks, a few commercial products attempted to popularize it in subsequent years. For instance, Atari introduced a phone featuring similar technology, later bought up by Mitsubishi and sold as the Luna around 1986. Despite the devices' affordability, no less than $400 in 1982, the cost of calls and the high price tag made them an unpopular choice.
The DIY picture phone project required numerous Integrated Circuits (ICs) on a tightly-packed double-sided printed circuit board, making it unsuitable for beginners. It used MM5280 dynamic RAM chips, which boasted a substantial 4,096 bits of memory, a considerable investment at about $5 each in 1982. The project was not a cheap endeavor by today's standards, with the estimated cost of the camera alone reaching $150.
Entire kits or key parts were available for purchase, with components often sourced from Robot Research, a company renowned for creating SSTV equipment for hams. The system had two primary inputs: fast scan from the camera and slow scan from the phone line, both capable of being digitized and stored in the memory array for later transmission.
The input conversion was handled by comparators and required just 16 ICs for monochrome conversion, considering the reduced complexity in comparison to contemporary projects. Memory speed was a concern, with each memory chip's enable line activating midway through the previous chip's cycle.
The device's main board, filled with gates, op amps, bipolar transistors, and other components, spoke volumes about the level of technical expertise required for its construction. For those interested in the system's intricacies, additional details can be found in the subsequent parts of the series.
While the idea of a direct, home-built connection to phone lines was illegal at the time, users could record the tones onto a cassette tape for later playback. It remains unclear how many pairs of these picture phones were constructed, although the magazine reportedly planned to publish a directory of users.
The dream of a widespread video phone remains unfulfilled, with our contemporary attempts falling short of the technology imagined in the 1980s. However, replication of this DIY picture phone using modern tools such as GNU Radio is a possibility, offering a fascinating glimpse into the past and a chance to bring this historic technological achievement to life in the present.
In 1982, a DIY project for constructing a picture phone, using technology such as closed-circuit TV cameras and ham radio-style slow scan TV (SSTV), was published in the Radio Electronics magazine, showcasing the capabilities of electronics and gadgets back then.
The creation of this historical DIY picture phone involves numerous Integrated Circuits (ICs) and advanced electronic components, making it a challenging project for electronics enthusiasts and technology enthusiasts interested in DIY electronics and gadgets.
