Thick Film
2512 Surge Resistors
BSR Series
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1.2/50 microsecond 250V pulse
10/700 microsecond 250V pulse
Nickel barrier terminations
Double glass passivation
Applications
Telephone lines are often subject to a variety of voltage disturbances
which fall into two main categories - short duration, high voltage
transients caused by lightning strikes and longer duration, over
voltages which may be caused by direct connection to mains power
lines. The advent of electronic switching has meant that sophisticated
methods of protection against these two fault conditions has to be
incorporated to ensure that potential damage is limited.
The two types of protection are: primary, which attempts to deal
with the bulk of the energy from a fast transient, particularly
lightning strikes and power crosses and secondary, which provides a
further level of protection to prevent damage to sensitive electronic
circuits.
The possibility of disturbances in the line is dependent on the envi-
ronment of the equipment installation. In the case of a PABX, where
the telephone line, terminal equipment and the line interface are all
installed in the same building, the possibility of induced lightning
transients is greatly reduced and the opportunity for damage induced
by direct connection to mains is low. For these reasons the degree of
protection is much less than for equipment connected outside the
building where the risk increases dramatically.
BI Technologies is involved in secondary protection for
all types of environment. The BSR Series has been specifically de-
signed for PABX where cost is of paramount importance. For central
switches, the tip and ring resistors are expected to perform identically
to maintain the correct resistance for a balanced line system. Both
resistors are therefore generally produced on a common substrate,
which may be through hole or surface mount, and perform close to
one another under all foreseeable fault conditions in both common
and differential modes. For PABX, tracking is not required because an
individual resistor is used which normally runs at low power yet has
the ability to withstand considerable power for long periods and has
good characteristics under high voltage transient conditions.
The BSR Series is a surface mount chip resistor in a standard 2512
package which utilizes special resistor film to handle the high voltage
with sophisticated laser trimming to prevent flash over. In the event
of a very high voltage pulse the resistor will go open-circuit prevent-
ing damage to surrounding components or the printed circuit board.
Two units are required for each incoming line to protect both tip and
ring individually and collectively. The resistor is made from nonflam-
mable material.
Electrical
Surge Capability, Max.
Standard Resistance Range, Ohms
Standard Resistance Tolerances
Operating Temperature Range
Temperature Coefficient of Resistance, Max.
Power Ratings, Watts, at 70°C ( See Note )
Operating Voltage, Max.
Note: For 2 watts limit part temperature to +155°C
S1.2 / 50 μs, 250 V; 10 / 700 μs, 250 V (ΔR ±5%+0.1Ω)
0.05 to 10K Ohms
±5%, ±10%, ±20% Optional : ±1%, ±2%
-55°C to +125°C
±100ppm/°C above 10 Ohms
1 and 2
100 V dc or
√PR
whichever is less
General Note
TT electronics reserves the right to make changes in product specification without notice or liability.
All information is subject to TT electronics’ own data and is considered accurate at time of going to print.
www.bitechnologies.com www.irctt.com www.welwyn-tt.com
© TT electronics plc
03.12
Thick Film
2512 Surge Resistors
BSR Series
Environmental
Short Time Overload, Max.
Temperature Cycling
Moisture Resistance
Load Life
Resistance to Solder Heat
2.5 x rated voltage (ΔR ±1%+0.1
Ω)
-55°C to +125°C, 5 cycles (ΔR ±5%+0.1
Ω)
1,000 hours at 40°C, 95% RH (ΔR ±3%+0.1
Ω)
1,000 hours at 70°C + Rated Voltage, Max. (ΔR ±3%+0.1
Ω)
260°C for 10 sec. (ΔR ±5%+0.1
Ω)
Construction
Glass Passivation:
Glass Protective
Coating
Resistor:
Ruthenium Oxide
Tin Plating
Nickel Barrier
Substrate:
Alumina
Thick Film Conductor
General Note
TT electronics reserves the right to make changes in product specification without notice or liability.
All information is subject to TT electronics’ own data and is considered accurate at time of going to print.
www.bitechnologies.com www.irctt.com www.welwyn-tt.com
© TT electronics plc
03.12
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