The SAK52 is identical to the SAK51. The added audio function (micro-phone and loudspeaker) supports 

Operating power (nominal)- 12 VDC via E-Bus
Current consumption: minimum34 mA
Current consumption: maximum115 mA
Special function keys - 6
Status LEDs - 5
LCD-display - 2 x 16 characters
Operating temperature - 0 +55 °C 
Housing protection - IP30
Dimensions (W x H x D) - 170 x 110 x  30 mm
Weight - 0.250 kg