Telnet error - formatting as docs suggest - any thoughts?

Trying to use telnet to turn some projectors on and off
followed the docs but get this error;

2018-05-17 12:42:43 ERROR (MainThread) [homeassistant.config] Invalid config for [switch.telnet]: required key not provided @ data[‘switches’][‘projectorl01’][‘value_template’]. Got None. (See ?, line ?). Please check the docs at

  - platform: telnet
        name: projectorl01
        resource: ""
        port: 23
        command_on: "PWR1"
        command_off: "PWR0"
        # command_state: "PWR?"
        # value_template: '{{ value == "PWR=01" }}'    

command state and value template are listed as optional in the docs so i haven’t used them. This is my first time using telnet in HASS so any local knowledge would be appreciated.

ps the dash is because i have other switches (command line, mqtt) below

i uncommented the value template and the log error vanished.
perhaps value template isn’t optional after all…