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NORTHEAST ELECTRONICS
COP.FORATION
Airport Road
Conccrd, New Hampshire
MODEL TTS
26ECD
PULSE SIGNALING
TEST SET
This addendum covers the description, operating instructions,
schematic, and table of replacement parts for the Model TTS
26BCD
Pulse Signaling Test Set.
General
The Model TTS
26BCD
may be operated from either
a
24 volt or
48 volt DC power supply and features a TTS 26BXD Dial Adapter Acces-
sory Cover as standard equipment.
The unit is otherwise identical in description and operation
to the Model TTS
2 6 B .
A description of the Model TTS 26B is given
in Section 1.0 of
the Operating Instructions.
Performance and Specifications
Same as Section 2.0, except for a large current drain (approx-
imately 500 ma) when operating at 24 volts DC.
Controls and Jacks
Same as Section 3.0, except power supply jacks are designated
24V or 48V.
Circuit Description
With the.exception of the 24 to 48 volt change-over circuitry,
the operation of the Model TTS
26BCD
is the same as described in
Section 4.0.
All of the switching to perform the 24 to 48 volt change-over
is accomplished over contacts of relay
K8.
Relay K8, when released,
establishes the proper circuit conditions for 24 volt operation and,
when operated, establishes the proper circuit conditions for 48 volt
operation.
When the unit is operated from a 24 volt power source, relay
K8
remains released.
Thus, internal circuits are arranged for 24 volt
operation.
When 48 volt power is applied to the unit, relay
K8 op-
erates and establishes the proper circuit conditions for 48 volt
operation.
The voltage required to operate relay K8 is in the order of 35
volts,
but
the set must be operated over 48 volts for proper callbra-
tion.
At 24 volt operation the set may be calibrated between
20
and
28 volts.
(over)
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