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Basic modules

4NSA. LF Interface Module, 4-Wire

4NSA. LF Interface Module, 4-Wire

The low frequency (LF) interface module is designed for the switching on of 4 call stations in four-wire technology.

At a Glance:

  • Switching-on of up to four call stations
  • Call station monitoring from the control unit
  • Monitoring of call station voltage
  • LF monitoring function (special model)
  • Establishing long-distance lines
  • Sending/receiving level can be regulated
  • Special functions (optional)

The principle functions of the 4NSA are illustrated in the following block diagram.

Block diagram 4NSA
Fig. Block diagram 4NSA

The 4NSA has four independent sets. One call station with two wire pairs can be connected to each set. If the 25 W booster amplifier of a call station is activated or connected then two additional wires are necessary for voltage supply.

With a four-wire connection, jumpers on the backplane are necessary for the supply.

The voltage feed (-48 V) of each 4NSA set is fused with a 1.6 A fuse. If a fuse has been triggered then the fuse LED switches off on the front plate and a message is sent to the processor module CPU1.

The functionality of the LF module can be programmed per set using the configuration software ICS. Control frames are sent bidirectionally over the modem line (Sa/Sb) cyclically between the 4NSA set and a call station. If a subscriber (call station) is absent then an error frame is sent to the CPU and the sending/receiving LED blinks slowly. This monitoring function can be disabled in the ICS.

The analogue voice signal from the LF line (La/Lb) is digitized on the 4NSA and transmitted to the PCM bus.

The mode of operation is set in the configuration software ICS:

  • Call station operation mode: One call station is expected as subscriber
  • Master operation mode: As counterpart a 4NSA as slave is expected
  • Slave operation mode: As counterpart a 4NSA as master is expected
  • No modem operation mode: The 4NSA only transmits LF signals

A slide-in attachment on the 4NSA as well as a special call station are necessary in order to realize the LF monitoring function.

For this an audio signal is generated cyclically over the microphone of the call station and sent to the 4NSA. If the transmission of the LF signal fails, then an error message is generated.

This mode is activated by ticking the option in ICS.

The Symbols on the Front Plate and their Meaning:

The System Blinker The System Blinker
Addressing from processor taking place
I/O Input/Output
BUS output works as push-push operation with the system blinker
BUS input works as push-pull operation with the system blinker
S/R Sending/Receiving (depending on the set)
LED lit: 4NSA sending to subscriber
LED blinking: 4NSA receiving from subscriber
LED blinking slowly: modem connection disrupted
FUSE Fuse (depending on set)
LED off: fuse has been triggered

Technical Data:

Operating Voltage: +/-5 V (control)
Operating Current (+5V): 200 mA
Operating Current (-5V) 4 mA
Temperature Range: 0 C to 45 °C
Weight: 300 g
Installation Height: 3HE
Installation Width: 6TE