ARLEC 600:600 Audio PSTN Isolation Transformer

Minimum Purchase:
1 unit
Maximum Purchase:
5 units
Calculated at Checkout

This type of audio transformer is commonly used to interface communications equipment or any other audio source to the PSTN (Public Switched Telephone Network), landlines in other words.

It is a requirement that any equipment connected to the PSTN is electrically isolated from the network.

Designed with a limited audio bandwidth because the PSTN typically uses voice frequencies in the frequency range 300Hz to 3.5Khz

Arlec Audio Isolation Transformer

Model: 45035A

600:600 Ohm

Single winding Primary

Single winding Secondary

Max Level: 0dBm @ 300Hz

Insertion Loss: 1dB max @ 0dBm

Frequency Response: 300Hz - 10kHz

Return Loss: >15dB, 300Hz - 5kHz

Max Unbalanced DC: 60mA

4KV isolation primary-secondary

Design bandwidth approximately 3.5Khz (300Hz to 3.5Khz) for use on the PSTN although it may to possible to extend this frequency range a little without excessive frequency loss but as this is certainly not intended for use with broadcast quality landline audio (15Khz or even up to 22Khz) - this would be well beyond the design frequency range of this transformer.


Used but in excellent condition

Carefully desoldered from radio equipment leaving full length PCB pins available.



Removed from some specialised commercial radio equipment, providing electrical isolation between the RX/TX audio of the equipment and the "outside world" i.e PSTN

Known to be fully fuctional prior to removal and a DC Ohms test after removal confirms they are undamaged.

These transformers are commonly used in "landline interface units" and many radio equipment manufacturers supply these modules e.g Tait Communications


Supplied in sealed plastic

Tested as described in the description This item is not returnable