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Signals
15 points
You have the ability to communicate in a physical medium other than sound. It typically originates in biological rather than technological processes, and it can’t carry digital signals. Your range is short compared to Telecommunication, limited by the recipient’s senses.
There are several versions, none of which can take the Vague limitation. “Vague Communication” is a 0-point feature that can accompany the prerequisite trait.

Blinker
Prerequisite: Illumination (GURPS Power-Ups 2: Perks, p. 10).
Your communications take the form of series of light flashes, about as bright as a torch or flashlight. Receiving them requires vision or Detect (Light; Precise, +100%).

Chemical Messengers
Prerequisite: Discriminatory Smell (Emotion Sense, +50%).
Your communications involve release of a wide range of different molecules into the air or water. All living organisms emit vague signals, except those with Sanitized Metabolism (p. B101). However, the ability to interpret chemical signals is an aspect of Discriminatory Smell.

Color Changes
Prerequisite: Chameleon (Controllable, +20%).
Your communications involve changing the coloration of your skin in complex patterns. Receiving them requires vision. You can take the modifier Video (+40%), allowing you to produce high-resolution patterns that copy what you see in detail.

Electrical Pulses
Prerequisite: Vibration Sense (Active Electroreception) (p. 44).
Your communications involve emitting modulated series of electrical discharges, usually at frequencies comparable to those of the human voice. Receiving them requires Vibration Sense (Active Electroreception).

Under the Hood: Signals
The advantage Signals, in its various forms, represents the ability to “speak” in a medium other than sound. How much should this be worth?
The human ability to speak is a baseline ability that costs 0 points; the ability to make only animal noises is Cannot Speak, worth ‑15 points. Telesend costs 30 points, but Telesend (Vague, ‑50%) is worth just 15 points, and limits the user to general concepts and emotions. So 15 points seems a fair price for the difference between vague and non-vague communication.
On the other hand, while Telesend (Vague) costs 15 points, Mute is ‑25 points – 10 points less than Cannot Speak. And any person’s or animal’s emotional state can be detected by a race with Discriminatory Smell (Emotion Sense); it costs nothing to emit vague chemical signals. So rather than being defined as Signals with a limitation, other forms of vague, animal-level communication are each identified with whatever existing traits provide suitable capabilities.