In some communications circuits a phenomenon called duty-cycle distortionthat is, a distortion of the apparent duration of the pulses in clock signalscauses the circuits to read clock signals as having a different duration than intended. The system may include two or more devices which may be magnetically connected in a body lumen, for example the system may include a first device which may include an imager and a transmitter for transmitting in vivo data, and a second device which may include a sampling mechanism. The sleeve has an open end with a protrusion. The trypsin-inhibiting agent is preferably zinc oxide in combination with an acid so as to release a specified divalent cation, i.