A 1200 baud modem sold by UK peripherals firm KDS Electronics.
The following description was found on an eBay listing:
"This is an Original Extremely rare 1200 bps modem for the Amstrad CPC series of computers. The package consists of a KDS Electronics Serial Interface (which also contains the KDS Comm 5 software in ROM), once plugged into the expansion bus of the Amstrad the ROM is immediatly recognised and starts up the Comms software for the Modem from the integrated ROM. A lead is supplied to comnnect the actual Modem to the ROM Interface.
"The Modem comes with a built in mains connection lead and standard telephone lead, Once plugged into the mains and connected to the interface and a telephone connection the modem is ready for use, all software is built into the interface no discs or tapes are required (or supplied).
"The modem is a full duplex modem with settings for ANS, CCITT,ORIG, 1200-75 75-1200 ORIG, Bell and ANS. Red LEDs on the front display TX (transmission) RX (receive) Carrier and power. The software can be used with the presets already contained on ROM or user defined settings ( a basic knowledge of comms will be useful here) and includes a telephone book for you to store and use telephone numbers.
"The interface is provided with a through connector to allow you to plug in other expansion devices at the same time (i.e. DD1 disk drive, digitiser, EPROM writer) It certainly works fine with the DD1 connected and i have had a ROMBO VIDI connected at the same time without any problems."