In 1975, Krown Research introduced a telecommunications device for the deaf (TDD) called the Porta-Printer. Meryl Miller from Datanetics was approached by Ralph Krongold of Krown Research—who he had met previously—with a request for help in producing the keyboards for this device. Meryl designed a keyboard using Datanetics DC-50 switches. He also produced the PCB artwork and had one of his vendors fabricate the PCBs. The keyboards themselves were assembled by Meryl at home using components from Datanetics.
Subsequently, Datanetics’ sales manager Ray West contacted Futaba with the hope of signing them up as a customer. In the process, Datanetics discovered that Futaba already had their own switches, although at the time they did not offer alternate action or illuminated models; this may have been just before Futaba MD was introduced, as MD—which these keyboards used—did offer both of these options. Datanetics then entered some kind of agreement to market the Futaba switches; Meryl Miller is no longer clear on the specifics of this arrangement. The end result however was that he designed a new model of keyboard for the Porta-Printer, built around MD switches, and assembled by Datanetics as a series of small orders.
At some point, Krown Research began assembling the keyboards themselves; it is not clear whether this was the older Datanetics type or the newer Futaba type.
The photographs below show three Porta-Printer keyboards that Meryl retained in his personal collection, as well as two spare PCBs, one designed for Datanetics DC-50 switches and one designed for Futaba MD switches.
The version using Datanetics switches uses a Harris Semiconductor HD1-0165-5 keyboard encoder and a Motorola MC14023B triple 3-input NAND gate. Harris’s HD-0165 is a static 16-key encoder, with a dedicated input for each switch. The Porta-Printer keyboard however has 31-keys. It’s possible that the HD1-0165-5 model, although the same size as the HD-0165 (DIP-24) has a different behaviour. The intention with the HD-0165 is that larger keyboards would use a pair of encoders, one per output nybble, with dual-output switches, which is not the case here.
A single photograph of the Krown Manufacturing Porta-View PV20 shows it to have Alps clone switches. Following an enquiry, Krown Manufacturing incorrectly described these as a “generic version of a Cherry switch”, and refused to name the manufacturer. The actual manufacturer is more likely to be Xiang Min (based on the plunger colour and position of the mould cavity numbers), but due to the clones of clones and other strange Far East manufacturing practices, it is impossible to be certain.