Wink is used both in connection with DC signaling on a trunk, and with indicator lamps on a key telephone.

In telephone switching systems, wink pulsing is recurring pulsing

Pulsing

Pulsing may refer to:* Pulsing * Pulse...

 in which the off-condition is relatively short compared to the on-condition. In Wink start trunks, the exchange at the originating end sends an off-hook

Off-hook

In telephony, the term off-hook has the following meanings:# The condition that exists when a telephone or other user instrument is in use, i.e., during dialing or communicating. Note: off-hook originally referred to the condition that prevailed when telephones had a separate earpiece , which hung...

 to alert to a call. The terminating end indicates readiness to receive the dialed telephone number

Telephone number

A telephone number or phone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short — as few as one, two or three digits — and were given orally to a switchboard operator...

 by sending an off-hook of approximately half a second duration, or "wink". Upon receiving this go ahead signal, the originating end uses multi-frequency

Multi-frequency

In telephony, multi-frequency signaling is an outdated, in-band signaling technique. Numbers were represented in a two-out-of-five code for transmission from a multi-frequency sender, to be received by a multi-frequency receiver in a distant telephone exchange...

 or other address signalling to send the phone number.

On 1A2 key systems

1A2 Key System

The 1A2 Key System is an analog multiline business key telephone system. Unlike more modern multiline systems, every telephone line serving a particular phone is wired into that phone, and electromechanical switches switch the lines in the phone itself...

 or similar key-operated telephone instruments, the hold position, i.e., the hold condition, of a line

Telephone line

A telephone line or telephone circuit is a single-user circuit on a telephone communication system...

 is often indicated by winking the associated lamp at 120 impulses per minute. During 6% of the pulse period the lamp is off and 94% of the period the lamp is on, i.e., 30 ms (milliseconds) off and 470 ms on.