An IS portable radio designed to the standard can
provide all the features and performance of a non-IS
model. It will also have a number of enhancements
and methods of protection to prevent explosions.
• full encapsulation of battery circuitry to prevent
electrolyte ingress in the unlikely event of a cell rupture,
• use of anti-static material for the battery case,
• stored energy limitation in the radio circuit,
• prevention of internal sparking or overheating,
• component and conductor spacing to prevent short
circuit caused by dust or atmospheric contamination.
The IEC 60079-11 standard covers both the radio
and battery and, if the battery is to be removable
in a hazardous environment, it must be completely
intrinsically safe in its own right. Not every radio brand
has this degree of battery protection – check with your
Here’s how IS protection is achieved
At the heart of the battery is a Lithium-Ion cell pack,
with thermal cut-outs, and a cell condition monitor to
prevent it being overcharged, or discharged too much.
An IS charge contact isolator ensures that no energy can
appear at the exposed charge contacts in normal use.
Supply is fed to the radio via an IS current limiter and IS
surge clamp. This will prevent arcing, should the battery
terminal be shorted or the battery disconnected from the
radio while it is in operation.
All IS circuit blocks are multiple-redundant, and the
entire circuit is encapsulated, to exclude atmospheric
contamination and electrolyte ingress, should a cell leak.
The radio power input also has an IS surge clamp. An IS
power limiter divides power between the high-current
transmitter power amplifier and an IS step-down voltage
regulator that supplies the rest of the radio. All IS blocks
INTRINSICALLY-SAFE PORTABLE RADIOS
power source KEY: IS multiple redundancy
rated to Ex IS