Radio Remote Control Unit
for Sony MZ-R30 Portable

Brian Houghton ([email protected])


With my choral activities I had a need to be able to switch the MZ-R30 from 'standby' to 'record' from a remote position within the choir. I looked at various methods, radio, infra-red, etc. The decision was made by the free availability of a redundant "Homecall" unit from a friend. This is normally used to summon aid when the operator presses a button on the pendant transmitter and the receiver, having established a coded identity, calls a central office. This unit has a range of 50ft, but can be extended to 100ft with a small whip aerial.

The MZ-R30 comes with a cable operated remote. In order to simulate the operation of the standby button I would need to break into the cable and place a resistance of 5156 ohms across the relevant pins. Incidentally, a new remote costs around GBP 58 and you can't buy the special plug for the MZ-R30.


The active pulse from the "Homecall" receiver drives a BC109 transistor to call a 12V DPDT relay. One set of contacts places the "Standby" control resistance across the appropriate pins on the remote connector via a modified remote cable. The other contacts operate a high brightness red filament indicator to signify to the user that the unit has operated. This contact is also used to clock a 4013 "D" type bistable which is used to control a green LED, either to flash at 2Hz to indicate "standby" similar to the MZ-R30 red record LED indicator, or as a steady state to indicate recording. Extra components are used to ensure that the bistable powers up in a "Standby" condition and to ensure positive changeover in the presence of the noisy pulse from the relay. The headphone output is repeated on the unit in case it is required to monitor whilst setting up. The 12 Volt power is provided by an external jelly battery.


The "Homecall" receiver and other components are fitted into a plastic project box which is placed on a photographic tripod by means of a "flash adapter". Alternative Transmitter/Receiver units could be sourced from Maplin UK. Typical units work on 173 or 418 Mhz and are low power units, normally used for garage doors, remote door bells, etc., that do not need a licence.

The existing remote cable is disconnected from the control pod and reconnected to a male mini XLR 5 pin connector. (These connectors are expensive, but are worth every penny. Don't be tempted to use mini-DIN connectors). This end will then mate with a female chassis XLR socket on the unit. A new cable is then made up using 5 thin wires in a 1/8" heatshrink sleeve. This will shrink down to the same size as the original cable to enable the control pod to be connected at one end and a female mini XLR 5 pin connector at the other. This enables the cable remote to be used in its original mode.



Perhaps one should write on the box "THIS IS NOT A BOMB!" It occurred to me that a member of the public who wasn't aware of the function of the unit could misunderstand with embarassing consequences.

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