23
Optical
The optical output is generated from a high power LED or Laser coupled to an
optical fiber. User connections are made at a bulkhead type ST connector at the
rear panel. The transmission fiber must be matched to the fiber pigtail type
specified at the time of manufacture. The input uses a pin diode and amplifier to
convert the optical signal back into an electrical signal. The optional single-fiber
system uses a wavelength division multiplexer to combine and then to separate
the two colors used. The main circuits in the Adder 882i are described in Table 8.
The basic setup is illustrated in Figure 2 on page 8.
A/D
High speed analog to digital converters located in each intercom
Multiplexer
Sequentially presents 8 RS-422 digital inputs and 8 digitized audio
signals from the A/D converters to the optical output driver
De-Multiplexer
Takes sequential digital signals from the PIN diode and separates
them into 20 separate line; 8 to the D/A converters and 8 to the RS-
422 transmitters
D/A
High speed digital to analog converters located at each audio
channel convert the digitized signal back to analog audio
Battery
Charge
The battery charger, Figure 18, is active whenever the 882i is
receiving DC power between 12-24VDC. Charging current is limited
to a trickle level. Full charge will take 16 hours.
Table 8: Adder 882i Main Circuits
Figure 17: Battery Charging Block Diagram
