2.3.7 The housing protruding from the Converter
field wires are inserted. The unit can be operated
back contains lightning arrestors for each field
with or without the back cover. The front cover must
t e r m i n a t i o n . The case of the Converter can be
be removed to gain access to the front control panel.
grouned to earth ground by running a strap from the
terminal labeled EARTH GROUND (on the back of
2.3.3 Figure 2 is a photograph of the front control
the Converter) to an earth grounding stake. Field
panel of the Converter with the front cover removed.
operation requires this path to earth ground for the
The common module contains the keysender, DTM -
F, and seize oscillator circuitry, the night alarm
from the Converter ease (floating ground) to prevent
(audible), the night alarm on-off switch and volume
control, the seize and release pushbutton switches,
2.3.8 The assembled unit is waterproof, airtight, and
the power on-off switch, the battery enclosure, and
shock resistant, and has been subjected to severe
the common circuit printed wiring board (PWB)
testing at the factory before shipment to the field.
assembly. The other three modules are individual
2.3.9 The Converter operates in conjunction with
channel modules and are identical in circuit
either the SB-22 ()/PT or SB-86()/P. Connection
operation. All channel modules are interchangeable.
between the Converter and either of these two units
T h e module closest to the common module is
can be made by plugging either the answer cord from
designated as Channel 1, the center module Channel
one of the manual switchboards or the cord from the
2 and the end module Channel 3. Each channel
operators' cord circuit into either jack on the front
module contains the service request indicator (SRI),
panel of the particular channel being utilized.
an access switch, two paralel wired telephone jacks,
2.3.10 An audible alarm is provided to alert the
and a channel PWB assembly. A defective channel
operator of an incoming call.
module can be removed for servicing while the
2.3.11 A volume control and an on-off switch (which
Converter is in use without impairing the operation
is an integral part of the volume control) is provided
of the other two channels. For proper removal and
on the front panel to allow control of the volume of
replacement procedures, refer to the maintenance
the night alarm signal, and to turn the night alarm
section of this manual.
off or on at the operator's discretion.
2.3.4 The battery compartment allows for easy
2.3.12 The service request indicator, flag type,
accessibility to the batteries from the front panel.
provides a visual indication of a request-for-service
For proper removal and replacement procedures,
on a particular channel. The flags on the indicator
refer to the maintenance section of this manual.
are coated with a phosphorescent material to allow
2.3.5 The front panel of the Converter is constructed
the indicator to be seen at night without the aid of a
of aluminum and has a gray semi-gloss finish. The
combination case is constructed of steel.
2.3.13 A power on-off switch allows the operator to
2 . 3 . 6 With the back cover removed, field ter-
minations are accessible and the instruction plate is
disconnect the batteries from the internal circuitry
when the Converter is not in use. The power ON-
visible (see Figure 3). Basic operating and con-
OFF switch is a locking, bat-handle switch designed
nection instructions are contained on the instruction
to prevent the operator from accidently bumping the
plate. For detailed operating instructions, refer to
switch to the OFF position during the operation of
the operating procedures in this manual. The field
the Converter. Refer to the operational procedures
terminations are identified as the converter send and
section of this manual for normal operation of the
converter receive pairs and by the associated channel
bat-handle on-off switch.
of the Converter to which they are connected. A
positive and negative battery terminal at the back of
For access to the lightning arrestors and for
the Converter allows the user to check battery
removal of the modules, refer to the
voltage or to use an external power supply (with the
maintenance section of this manual.
batteries removed) for maintenance of the Converter
at the depot. The additional terminal on the back of
the Converter is for earth ground.