|The Type A was
already being used by the NZ Army with the existing Wireless Sets No. 1
and No. 11 so was a logical choice for the ZC1 Mk-1 as well.
when the ZC1 Mk-2 was developed the circuit of the Type A appears to
have been slightly simplified and other changes made such as the
use of the No.8 microphone. The modified RCU was renamed as the
ZC1 Mk-2 RCU.
Generally the two RCUs are close to identical in appearance and most
parts with the exception of the microphones interchangeable.