The term modular connector is the name given to a family of electrical connectors originally used in telephone wiring and are now used for a variety of other things as well. 

Advantages of modular connectors include small size and ease of connecting.  Many devices that originally used a bulkier connector have migrated to modular connectors. Probably the most well known applications of modular connectors is for telephone jacks and or Ethernet jacks, which are nearly always modular.

Warner Instruments' TC-124/144 temperature controllers accept modular connectors to power model WP-10 and WP-16 warmed platforms, OW series objective warmers, and SWS Series syringe warmers.  Two typical modular connectors are shown below.