1970's AUSTRALIAN HANDSET (with Push To Talk switch)

Grey Handset WITH INTEGRAL PUSH TO TALK SWITCH

Commonly used with the old radio telephone systems that used landlines out to the radio user subscribers and also some specialised telephone systems that required transmit control by the user.

This handset has a 6 wire curly cord, (an extra pair for the PTT) unlike a standard handset with only 4 wires.

This handset is designed to use the smaller dynamic coil based receiver insert and the transmitter insert is the carbon based transmitter.

Transmitter - STC #13 Capsule
Carbon based i.e as you talk into the microphone, the carbon granules move and the resistance changes in sympathy with the sound waves.
At rest, the transmitter element measures 800 Ohm but immediately changes when the user speaks into the transmitter.

Colour code at the end of the curly cord for the transmitter is Orange & White

Receiver - STC #200930 Capsule
Dynamic receiver element
Unlike the transmitter, this is used like a very small speaker
DC resistance is 430 Ohm

Colour code at the of the curly cord for the receiver is Blue & Green

Push To Talk Switch - Den Dee Made In Melbourne
This is a SPST microswitch, mounted on the side of the handset.
Non-locking i.e push on, release off
2 Ohm resistance when activated (button pushed)

Colour code at the end of the curly cord for this switch is Black & Red

COSMETIC CONDITION:
Very good - no damage or cracks but there is light discolouration/plastic colour fade.

TESTING:
Tested all elements of the handset - everything is good.

Great as a museum piece or press it into service for a custom project. All elements of the handset are accessible individually (no common wiring) so it would not be hard to use this with radio communications equipment although it is likely a different microphone insert may need to be fitted (dynamic or electret) instead of the carbon microphone,  or quickly make up a suitable interface by using either a battery supply with an audio  transformer or an equivalent circuit using a semiconductor - have a look around online, lots of circuit design ideas for using old carbon microphones.