Module A-148 (Dual S&H) has two identical sample & hold modules, designed to produce 'staircase' voltages. The signal present at the sample input is sampled at a rate set by the signal at the trigger input, and held at that voltage at the S&H output. 
The exact shape of the staircase depends on the sort of waveform at the sample input: NOISE or RANDOM signals produce random patterns; an LFO produces rising or falling staircase patterns. 
Two LEDs for each S&H indicate the voltage (positive or negative) of the sampled signal.

For more detailed information please look at the English user's manual: A148_man.pdf 

Similar modules: A-152 Voltage Addressed Track&Hold / Switch (Multiplexer) / Digital Outputs

Since August 2005 an improved version of the module is manufactured: For each sub-module the operation mode S&H (sample&hold) or T&H (track&hold) can be selected by a jumper. In T&H mode the output signal follows the input signal while the trigger input is "high". As soon as the trigger input turns to "low" the last voltage is stored. The factory setting is S&H for the upper device and T&H for the lower device. At the bottom of this page the function of the jumpers is described. In addition the complete A-100 voltage range -12...+12V can be processed (no longer limited to -8...+8V as for the previous version).
The two versions can be identified by these details:
Version 1: four integrated circuits (2 x CD4053, 2 x TL064 oder TL084)
Version 2: three integrated circuits (1x DG442, 2 x TL084), see silk screen at the bottom of this page.

Breite/Width: 4 TE / 4 HP / 20.0 mm
Tiefe/Depth: 30 mm (gemessen ab der Rückseite der Frontplatte / measured from the rear side of the front panel)
Strombedarf/Current: 20 mA