* signals_density    - setting to put signal on every Nth tile (double space on |, -- tracks)

	 **********

	 * trackdir   - trackdir to build with autorail

	 * semaphores - semaphores or signals

	 * signals    - is there a signal/semaphore on the first tile, copy its style (two-way/single-way)

	 *              and convert all others to semaphore/signal

	 * remove     - 1 remove signals, 0 build signals */

	int signal_ctr = 0;

	CommandCost last_error = CMD_ERROR;

	bool had_success = false;

	for (;;) {

		/* only build/remove signals with the specified density */

			uint32 p1 = GB(TrackdirToTrack(trackdir), 0, 3);

			SB(p1, 3, 1, mode);

			SB(p1, 4, 1, semaphores);

			SB(p1, 5, 3, sigtype);

			if (!remove && signal_ctr == 0) SetBit(p1, 17);

			/* Pick the correct orientation for the track direction */

			signals = 0;

			if (HasBit(signal_dir, 0)) signals |= SignalAlongTrackdir(trackdir);

			if (HasBit(signal_dir, 1)) signals |= SignalAgainstTrackdir(trackdir);

			CommandCost ret = DoCommand(tile, p1, signals, flags, remove ? CMD_REMOVE_SIGNALS : CMD_BUILD_SIGNALS);