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TTM 01-G Manual / October 2018
17
Isolation and Protection
The GNSS Antenna input is earth referenced. Care should be used when installing to prevent earth currents
circulating in the antenna cable. The TTL output features an earthed, non-isolated driver and is designed for
connection within the same rack. Since it is the only output with an earth reference, it is isolated from the
power supply via the power supply isolation, and from all other I/O by their isolation. All the other outputs are
galvanically isolated (including the optional TTL output card) from the internal electronics and power supply.
The Alarm port has a UL and VDE approved 3.75 kV isolated contact and is protected by a 600 V, 175 mA self-
resetting fuse and a 350 V transient suppressor diode.
The copper Ethernet port provides 1.5 kV isolation and includes Electro-Static Discharge (ESD) suppression on
board.
All optional output cards feature at least 3 kV isolation from earth and have ESD suppression suitable for the
interface type.
The power supply isolation varies from 1.6 kV for low and medium voltage power supplies to 3 kV for the high
voltage power supply. In addition, isolation protects the internal electronics from longitudinal transient voltages
and transient suppression devices protect from transverse transient voltages.