BCD Audio has designed audio products since 1987, mostly to serve the Broadcast industry.
At that time, most audio was analogue, and a range of analogue audio Eurocards were introduced to matching the system requirements of the day. The 1U ‘Amplifier System’ rack box was designed to accommodate up to 4 Eurocards, with local front panel controls.
Always comfortable with microcontrollers, a two wire control system across 32 Eurocards with a common control card simplified the rack control system. Analogue and relay switcher cards to 16*8 size were designed, and a reliable RS485 control system capable of up to 63 control panels introduced. This is known as the RMOS ( Ring main & Outside Source ) system.
By 1999, Digital Audio using SPDIF and AES3 were common, and we noticed that most companies were producing one module per Eurocard and we wondered if we could pack more into each eurocard by using sub-modules. These became known as ‘Piglets’ ( Short for Piggy back cards) and a Eurocard designed to take 3 Piglets.
Piglets that required clocking uses the Installer-Full Eurocard that includes a microcontroller for booting and supervision, and a clock synthesiser for Wordclock and AES3 reference signals.
Simpler DA type and Digital to Analogue Piglets could use a simpler dumb Eurocard, and this is known as the Installer-Basic Eurocard.
The Installer-12 1U frame was designed to take up to 12 Piglets over 4 Eurocards, and the Installer-48 3U frame was designed to take up to 48 Piglets over 16 Eurocards, hence the names.
Later, the Installer-12 frame was replaced by the Installer-4 frame to reduce cost, but actually came in more expensive!
The frames included dual power supplies, and could mix dedicated Eurocards with Installer + Piglet Eurocards. The RMOS and RS485 ideas are used when required, and a common wordclock input was often used.
The PAM system is an example of the Installer-48 and uses the RMOS control system.