AKG PCC170 SWO Boundary Microphone with Remote Switch Sensing Leads

AKG PCC170 SWO: A Boundary Microphone That Tells the Room What It Is Doing

The AKG PCC170 SWO is a half-supercardioid boundary layer microphone whose cable carries a pair of extra leads allowing isolated remote sensing of the microphone switch closure. Acoustically it matches its switched sibling with 22 mV/Pa sensitivity, 22 dB-A equivalent noise, a 72 dB-A signal-to-noise ratio and a published 50 Hz to 20,000 Hz bandwidth on 12 to 48 V phantom power. The addition is not another feature on the audio path; it is a second, electrically separate path that turns each table position into a source of information as well as a source of sound. That single difference is what makes this the version integrators specify for automated rooms.

What an Isolated Switch Closure Actually Provides

Sensing a switch remotely sounds trivial until the alternatives are examined. Reading a microphone's state from its audio, by detecting whether signal is present, is guesswork, because a talker who is silent looks identical to a talker who is muted; reading it from the same conductors that carry the audio risks injecting switching artefacts straight into a balanced pair that a preamplifier is amplifying by sixty decibels. Bringing the closure out on its own dedicated pair, electrically isolated from the audio, gives a control system a clean, unambiguous contact state with no reference to the audio ground at all. AKG does not publish a contact rating or an isolation voltage for these leads, so the sensible practice is to treat them as a dry contact input to whatever equipment is reading them and confirm the interface's own requirements.

Camera Presets, Tally and Logging Systems

Room automation is where the extra pair earns its place. A council chamber with a camera on a pan-tilt head can recall a preset the instant a particular seat's microphone opens, so the picture follows the debate without an operator; a courtroom recording system can write a talker-active flag alongside the audio so a transcriptionist knows which position was live at any moment; a broadcast or streaming setup can drive a tally light or an on-air indicator from the same closure. Distance-learning rooms use it to switch a display source when an instructor keys their microphone, and building systems use it to duck program audio automatically. In every one of these the microphone is the sensor, which removes an entire layer of manual operation from the room.

Contact Closure Versus Level-Based Automixing

Automatic mixers decide which channels to open, and how they decide matters enormously in a difficult room. A level-based automixer opens a channel when its input rises above a threshold relative to the others, which works well in a quiet space and badly in one with air handling, shuffled paper, laptop fans or a loudspeaker in the same room, because all of those can look like speech to a detector. Gating on a hard switch closure instead gives a deterministic answer: the channel is open because a person deliberately opened it, not because a microphone heard something. Many installations run both, using level detection for gain sharing and contact closure for absolute priority, and the extra leads on this microphone are what make the second half possible.

The Acoustic Engine and Boundary Mounting

Underneath the logic features sits the same surface-mount design the family is known for. A capsule placed in the boundary layer of a table receives direct sound and the surface reflection at effectively the same instant, so the two sum in phase and produce the smooth response a stand-mounted table microphone cannot manage, since its reflection arrives late enough to cancel parts of the speech band. The half-supercardioid pattern narrows the forward acceptance and places rejection nulls toward the rear, giving the best feedback margin in the surface-mount range for a room whose loudspeakers are live while microphones are open. A three-position bass-tilt switch handles subsonic rumble arriving through the table, and the microphone presents a balanced output on a 3-pin locking mini connector with a detachable cable terminating in a 3-pin XLR male.

When to Specify the SWO Instead of the SW

Both switched versions mute a position silently and light an LED locally, so the deciding question is simple: does anything outside the audio system need to know? If the answer is no, and a mixer with muted channels is the whole requirement, the plain switched model is the right part. If a camera, a control processor, a logging recorder, a tally circuit or an automixer priority input has to follow the switch, only the version with the extra sensing leads will do, because retrofitting that capability later means replacing the microphone. Integrators designing chambers, courtrooms and integrated boardrooms tend to specify the sensing version throughout for exactly that reason, even where only some positions are automated on day one.